Movable body drive method and movable body drive system, pattern formation method and apparatus, exposure method and apparatus, and device manufacturing method

ABSTRACT

Positional information of a stage within a movement plane is measured, using three encoders which include at least one each of an X encoder and a Y encoder. Based on position measurement values of the stage, the encoder used in position measurement is switched from an encoder (Enc 1 , Enc 2  and Enc 3 ) to an encoder (Enc 4 , Enc 2  and Enc 3 ). On the switching, a coordinate linkage method or a phase linkage method is applied to set an initial value of an encoder (Enc 4 ) which is to be newly used. Accordingly, position measurement values of the stage before and after the switching are stored even though the encoder used in position measurement of the stage is sequentially switched, and the stage can be driven accurately two-dimensionally.

CROSS-REFERENCE TO RELATED APPLICATIONS

This non-provisional application claims the benefit of ProvisionalApplication No. 60/935,385 filed Aug. 9, 2007, and ProvisionalApplication No. 61/006,795 filed Jan. 31, 2008, the disclosures of whichare hereby incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to movable body drive methods and movablebody drive systems, pattern formation methods and apparatuses, exposuremethods and apparatuses, and device manufacturing methods, and moreparticularly, to a movable body drive method and a movable body drivesystem that drives a movable body along a predetermined plane, a patternformation method using the movable body drive method and a patternformation apparatus equipped with the movable body drive system, anexposure method using the movable body drive method, and an exposureapparatus equipped with the movable body drive system, and a devicemanufacturing method using the pattern formation method.

2. Description of the Background Art

Conventionally, in a lithography process for manufacturing microdevices(electron devices and the like) such as semiconductor devices and liquidcrystal display devices, exposure apparatuses such as a reductionprojection exposure apparatus by a step-and-repeat method (a so-calledstepper), a scanning projection exposure apparatus by a step-and-scanmethod (a so-called scanning stepper (which is also called a scanner),and the like are relatively frequently used.

In these kinds of exposure apparatuses, in order to transfer a patternof a reticle (or a mask) on a plurality of shot areas on a substratesuch as a wafer or a glass plate (hereinafter, generally referred to asa wafer), a wafer stage holding the wafer is driven in a two-dimensionaldirection, for example, by linear motors and the like. Positionmeasurement of the wafer stage and the like was generally performedusing a laser interferometer whose stability of measurement values wasgood for over a long time and had a high resolution.

However, requirements for a stage position control with higher precisionare increasing due to finer patterns that accompany higher integrationof semiconductor devices, and now, short-term variation of measurementvalues due to temperature fluctuation of the atmosphere on the beam pathof the laser interferometer or the influence of temperature gradient hascome to occupy a large percentage in the overlay budget.

Meanwhile, as a measurement device besides the laser interferometer usedfor position measurement of the stage, an encoder can be used, however,because the encoder uses a scale, which lacks in mechanical long-termstability (drift of grating pitch, fixed position drift, thermalexpansion and the like), it makes the encoder have a drawback of lackingmeasurement value linearity and being inferior in long-term stabilitywhen compared with the laser interferometer.

In view of the drawbacks of the laser interferometer and the encoderdescribed above, various proposals are being made (refer to Kokai(Japanese Patent Unexamined Application Publication) No. 2002-151405) ofa device that measures the position of a stage using both a laserinterferometer and an encoder (a position detection sensor which uses adiffraction grating) together.

Further, the measurement resolution of the conventional encoder wasinferior when compared with an interferometer, however, recently, anencoder which has a nearly equal or a better measurement resolution thana laser interferometer has appeared (for example, refer to Kokai(Japanese Patent Unexamined Application Publication) No. 2005-308592),and the technology to put the laser interferometer and the encoderdescribed above together is beginning to gather attention.

For example, in the exposure apparatus, in the case of performingposition measurement of a wafer stage on which a scale (a grating) hasbeen arranged using an encoder, in order to cover a broad movement rangeof the wafer stage, it is conceivable that a plurality of heads areplaced at a predetermined interval within a two-dimensional plane.

However, in the case of using the plurality of heads having such aplacement, it is important to perform the switching of the head used forcontrol without disturbing the smooth operation of the wafer stage.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provideda first movable body drive method in which a movable body is drivenalong a predetermined plane including a first axis and a second axisorthogonal to each other, the method comprising: a first process inwhich a position coordinate of the movable body is obtained, based onmeasurement values of three encoder heads among a plurality of firstencoder heads whose position in a direction parallel to the second axisis different and a plurality of second encoder heads whose position in adirection parallel to the first axis is different, with the threeencoder heads respectively facing three gratings selected from a pair offirst gratings whose periodic direction is in a direction parallel tothe first axis and a pair of second gratings whose periodic direction isin a direction parallel to the second axis that are arranged on asurface parallel to the predetermined plane of the movable body; and asecond process in which a measurement value of an encoder head to benewly used is set again so that the position coordinate is maintainedbefore and after the switching of the encoder head.

According to this method, on the switching of the encoder head, theposition coordinate of the movable body is maintained before and afterthe switching.

According to a second aspect of the present invention, there is provideda second movable body drive method in which a movable body is drivenalong a predetermined plane including a first axis and a second axisorthogonal to each other, the method comprising: a first process inwhich a position coordinate of the movable body is obtained, based onmeasurement values of three encoder heads among a plurality of firstencoder heads whose position in a direction parallel to the second axisis different and a plurality of second encoder heads whose position in adirection parallel to the first axis is different, with the threeencoder heads respectively facing three gratings selected from a pair offirst gratings whose periodic direction is in a direction parallel tothe first axis and a pair of second gratings whose periodic direction isin a direction parallel to the second axis that are arranged on asurface parallel to the predetermined plane of the movable body; and asecond process in which only a measurement value by a measurement unitof an encoder head to be newly used after the switching is to be setagain, based on a position coordinate of the movable body.

According to this method, even in the case when the encoder head used inposition control (position measurement) of the movable body is switchedin succession with the movement of the movable body, errors do notaccumulate on each switching.

According to a third aspect of the present invention, there is provideda third movable body drive method in which a movable body is drivenalong a predetermined plane including a first axis and a second axisorthogonal to each other, the method comprising: a first process inwhich a position of the movable body within the predetermined plane iscontrolled, based on measurement values of a set of heads of an encoderincluding three heads among a plurality of first heads whose position ina direction parallel to the second axis is different and a plurality ofsecond heads whose position in a direction parallel to the first axis isdifferent, with the three heads respectively facing three gratingsselected from a pair of first gratings whose periodic direction is in adirection parallel to the first axis and a pair of second gratings whoseperiodic direction is in a direction parallel to the second axis thatare arranged on a surface parallel to the predetermined plane of themovable body; and a second process in which a set of heads used inposition control of the movable body is switched to a different set ofheads including three heads that have at least one head which isdifferent from the set of heads so that the position of the movable bodywithin the plane becomes successive before and after the switching.

According to this method, the position (including rotation within thepredetermined plane) of the movable body is maintained (the positioncoordinate is stored) before and after the switching of the set ofheads.

According to a fourth aspect of the present invention, there is provideda fourth movable body drive method in which a movable body is drivenalong a predetermined plane including a first axis and a second axisorthogonal to each other, the method comprising: a first process inwhich a position of the movable body within the predetermined plane iscontrolled, based on measurement values of a set of heads of an encoderincluding three heads among a plurality of first heads whose position ina direction parallel to the second axis is different and a plurality ofsecond heads whose position in a direction parallel to the first axis isdifferent, with the three heads respectively facing three gratingsselected from a pair of first gratings whose periodic direction is in adirection parallel to the first axis and a pair of second gratings whoseperiodic direction is in a direction parallel to the second axis thatare arranged on a surface parallel to the predetermined plane of themovable body; and a second process in which a set of heads used inposition control of the movable body is switched to a different set ofheads including three heads that have at least one head which isdifferent from the set of heads, using the offset by the measurementunit computed based on the position of the movable body and the offsetequal to or less than the measurement unit set for each head.

According to this method, even in the case when the set of heads used inposition control of the movable body is switched in succession with themovement of the movable body, errors do not accumulate on eachswitching.

According to a fifth aspect of the present invention, there is provideda fifth movable body drive method in which a movable body is drivenalong a predetermined plane including a first axis and a second axisorthogonal to each other, the method comprising: a first process inwhich a position of the movable body within the predetermined plane iscontrolled, based on measurement values of a set of heads of an encoderincluding three heads among a plurality of first heads whose position ina direction parallel to the second axis is different and a plurality ofsecond heads whose position in a direction parallel to the first axis isdifferent, with the three heads respectively facing three gratingsselected from a pair of first gratings whose periodic direction is in adirection parallel to the first axis and a pair of second gratings whoseperiodic direction is in a direction parallel to the second axis thatare arranged on a surface parallel to the predetermined plane of themovable body; a second process in which a set of heads used in positioncontrol of the movable body is switched to a different set of headsincluding three heads that have at least one head which is differentfrom the set of heads so that the position of the movable body withinthe predetermined plane becomes successive before and after theswitching, and also on the switching, a processing in which an offset bythe measurement unit of a specific head used only after the switching isdecided based on the position of the movable body, and an offset equalto or less than the measurement unit of the specific head is decided sothat the position of the movable body is coincident before and after theswitching, with the plurality of first heads and/or the plurality ofsecond heads serving as the specific head; and a third process in whichuntil the offset equal to or less than the measurement unit is updated,a set of heads used in position control of the movable body is switchedat every timing when switching of the set of heads occurring with themovement of the movable body becomes required to a different set ofheads including three heads that have at least one head which isdifferent from the set of heads, using the offset by the measurementunit computed based on the position of the movable body and the offsetequal to or less than the measurement unit kept for each head.

According to this method, until the offset by the measurement unit andthe offset by the measurement unit is decided so that the position ofthe movable body is coincident before and after the switching and theoffset equal to or less than the measurement unit is updated, the offsetby the measurement unit computed based on the position of the movablebody and the offset equal to or less than the measurement unit storedfor each head are used on the switching of the set of heads.Accordingly, even in the case when the set of heads used in positioncontrol of the movable body is switched in succession with the movementof the movable body, errors do not accumulate on each switching, andposition control of the movable body with high precision is alsopossible.

According to a sixth aspect of the present invention, there is provideda pattern formation method, comprising: a process in which an object ismounted on a movable body that can move in a movement plane; and aprocess in which the movable body is driven by the movable body drivemethod according to any one of the first to fifth movable body drivemethods of the present invention, to form a pattern to the object.

According to this method, by forming a pattern on the object mounted onthe movable body which is driven with good accuracy using any one of thefirst to fifth movable body drive methods of the present invention, itbecomes possible to form a pattern on the object with good accuracy.

According to a seventh aspect of the present invention, there isprovided a device manufacturing method including a pattern formationprocess, wherein in the pattern formation process, a pattern is formedon an object using the pattern formation method of the presentinvention.

According to an eighth aspect of the present invention, there isprovided an exposure method in which a pattern is formed on an object byan irradiation of an energy beam wherein for relative movement of theenergy beam and the object, a movable body on which the object ismounted is driven, using any one of the first to fifth movable bodydrive methods of the present invention.

According to this method, for relative movement of the energy beamirradiated on the object and the object, the movable body on which theobject is mounted is driven with good precision, using any one of thefirst to fourth movable body drive methods of the present invention.Accordingly, it becomes possible to form a pattern on the object withgood precision by scanning exposure.

According to a ninth aspect of the present invention, there is provideda first movable body drive system in which a movable body is drivenalong a predetermined plane including a first axis and a second axisorthogonal to each other, the system comprising: a pair of firstgratings whose periodic direction is in a direction parallel to thefirst axis and a pair of second gratings whose periodic direction is ina direction parallel to the second axis that are arranged on a surfaceparallel to the predetermined plane of the movable body; a first encodersystem which has a plurality of first heads whose positions aredifferent in a direction parallel to the second axis and measurespositional information of the movable body in a direction parallel tothe first axis, based on measurement values of the first headsrespectively facing the pair of first gratings; a second encoder systemwhich has a plurality of second heads whose positions are different in adirection parallel to the first axis and measures positional informationof the movable body in a direction parallel to the second axis, based onmeasurement values of the second heads respectively facing the pair ofsecond gratings; and a controller which obtains a position coordinate ofthe movable body within the predetermined plane based on measurementvalues of a set of heads including three heads respectively facing threegratings selected from the pair of first gratings and the pair of secondgratings, and sets a measurement value again of a head which is to benewly used so that the position coordinate is maintained before andafter the switching when switching the head to be used in positionmeasurement of the movable body.

According to this system, on the switching of the encoder head, theposition coordinate of the movable body is maintained before and afterthe switching.

According to a tenth aspect of the present invention, there is provideda second movable body drive system in which a movable body is drivenalong a predetermined plane including a first axis and a second axisorthogonal to each other, the system comprising: a pair of firstgratings whose periodic direction is in a direction parallel to thefirst axis and a pair of second gratings whose periodic direction is ina direction parallel to the second axis that are arranged on a surfaceparallel to the predetermined plane of the movable body; a first encodersystem which has a plurality of first heads whose positions aredifferent in a direction parallel to the second axis and measurespositional information of the movable body in a direction parallel tothe first axis, based on measurement values of the first headsrespectively facing the pair of first gratings; a second encoder systemwhich has a plurality of second heads whose positions are different in adirection parallel to the first axis and measures positional informationof the movable body in a direction parallel to the second axis, based onmeasurement values of the second heads respectively facing the pair ofsecond gratings; and a controller which obtains a position coordinate ofthe movable body in the predetermined plane, based on the measurementvalues of the set of heads including the three heads respectively facingthe three gratings selected from the pair of first gratings and the pairof second gratings, and sets only a measurement value by a measurementunit according to a head to be newly used after the switching again,based on the position coordinate when switching the head to be used forposition measurement of the movable body.

According to this system, even in the case when the head used inposition control (position measurement) of the movable body is switchedin succession with the movement of the movable body, errors do notaccumulate on each switching.

According to an eleventh aspect of the present invention, there isprovided a third movable body drive system in which a movable body isdriven along a predetermined plane including a first axis and a secondaxis orthogonal to each other, the system comprising: a pair of firstgratings whose periodic direction is in a direction parallel to thefirst axis and a pair of second gratings whose periodic direction is ina direction parallel to the second axis that are arranged on a surfaceparallel to the predetermined plane of the movable body; a first encodersystem which has a plurality of first heads whose positions aredifferent in a direction parallel to the second axis and measurespositional information of the movable body in a direction parallel tothe first axis, based on measurement values of the first headsrespectively facing the pair of first gratings; a second encoder systemwhich has a plurality of second heads whose positions are different in adirection parallel to the first axis and measures positional informationof the movable body in a direction parallel to the second axis, based onmeasurement values of the second heads respectively facing the pair ofsecond gratings; and a controller which controls the position of themovable body in the predetermined plane, based on the measurement valuesof the set of heads including the three heads respectively facing thethree gratings selected from the pair of first gratings and the pair ofsecond gratings, and also switches a set of heads used in positioncontrol of the movable body to a different set of heads including threeheads that have at least one head which is different from the set ofheads so that the position of the movable body within the predeterminedplane becomes successive before and after the switching.

According to this system, the position (including the position of therotational direction within the predetermined plane) of the movable bodybecomes continuous (is maintained) before and after the switching of theset of heads.

According to a twelfth aspect of the present invention, there isprovided a fourth movable body drive system in which a movable body isdriven along a predetermined plane including a first axis and a secondaxis orthogonal to each other, the system comprising: a pair of firstgratings whose periodic direction is in a direction parallel to thefirst axis and a pair of second gratings whose periodic direction is ina direction parallel to the second axis that are arranged on a surfaceparallel to the predetermined plane of the movable body; a first encodersystem which has a plurality of first heads whose positions aredifferent in a direction parallel to the second axis and measurespositional information of the movable body in a direction parallel tothe first axis, based on measurement values of the first headsrespectively facing the pair of first gratings; a second encoder systemwhich has a plurality of second heads whose positions are different in adirection parallel to the first axis and measures positional informationof the movable body in a direction parallel to the second axis, based onmeasurement values of the second heads respectively facing the pair ofsecond gratings; and a controller which controls the position of themovable body in the predetermined plane, based on the measurement valuesof the set of heads including the three heads respectively facing thethree gratings selected from the pair of first gratings and the pair ofsecond gratings, and also switches a set of heads used in positioncontrol of the movable body to a different set of heads including threeheads that have at least one head which is different from the set ofheads, using the offset by the measurement unit computed based on theposition of the movable body and the offset equal to or less than themeasurement unit kept for each head.

According to this system, even in the case when the set of heads used inposition control of the movable body is switched in succession with themovement of the movable body, errors do not accumulate on eachswitching.

According to a thirteenth aspect of the present invention, there isprovided a pattern formation apparatus, the apparatus comprising: amovable body on which an object is mounted that can move in a movementplane holding the object; a patterning device which generates a patternon the object; and a movable body drive system according to any one ofthe first to fourth movable body drive systems which drives the movablebody for pattern formation to the object.

According to this apparatus, by generating a pattern with a patterningdevice on the object on the movable body driven with good precision byany one of the first to fourth movable body drive systems of the presentinvention, it becomes possible to form a pattern on the object with goodprecision.

According to a fourteenth aspect of the present invention, there isprovided an exposure apparatus that forms a pattern on an object by anirradiation of an energy beam, the apparatus comprising: a patterningdevice that irradiates the energy beam on the object; and any one of thefirst to fourth movable body drive systems according to the presentinvention, whereby the movable body drive system drives the movable bodyon which the object is mounted for relative movement of the energy beamand the object.

According to this apparatus, for relative movement of the energy beamirradiated on the object from the patterning device and the object, themovable body on which the object is mounted is driven with goodprecision by any one of the first to fourth movable body drive systemsof the present invention. Accordingly, it becomes possible to form apattern on the object with good precision by scanning exposure.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings;

FIG. 1 is a view schematically showing the configuration of an exposureapparatus related to an embodiment;

FIG. 2 is a planar view showing a stage device in FIG. 1;

FIG. 3 is planar view showing placement of various measurement devices(an encoder, an alignment system, a multipoint AF system, a Z head)which exposure apparatus of FIG. 1 comprises;

FIG. 4A is a planar view showing a wafer stage, and FIG. 4B is aschematic side view of a partially sectioned wafer stage WST;

FIG. 5A is a planar view showing a measurement stage, and FIG. 5B is aschematic side view showing a partial cross section of the measurementstage;

FIG. 6 is a block diagram showing a configuration of a control system ofthe exposure apparatus related to an embodiment;

FIG. 7A is a view showing an example of a configuration of an encoder,and FIG. 7B is a view showing the case when a laser beam LB having asectional shape extending narrowly in the periodic direction ofdiffraction grating RG is used as a detection light;

FIG. 8 is a view showing a state of the wafer stage and the measurementstage when exposure to a wafer is performed by a step-and-scan method;

FIG. 9 is a view showing a state of the wafer stage and the measurementstage at the time of unloading of the wafer;

FIG. 10 is a view showing a state of the wafer stage and the measurementstage at the time of loading of the wafer;

FIG. 11 is a view showing a state of the wafer stage and the measurementstage, and the placement of encoder heads at the time of switching fromstage servo control by an interferometer to stage servo control by anencoder;

FIG. 12 is a view for explaining a state of the wafer stage and themeasurement stage at the time of the wafer alignment;

FIG. 13A is a view showing a Doppler effect that the light scattered bya movement plane receives, and FIG. 13B is a view showing aconfiguration of an encoder head section;

FIG. 14A is a view showing a case when a measurement value does notchange even if a relative movement in a direction besides themeasurement direction occurs between a head of an encoder and a scale,and FIG. 14B is a view showing a case when a measurement value changeswhen a relative movement in a direction besides the measurementdirection occurs between a head of an encoder and a scale;

FIGS. 15A to 15D are views used for describing the case when themeasurement value of the encoder changes and the case when themeasurement value does not change, when a relative movement in adirection besides the measurement direction occurs between the head andthe scale;

FIGS. 16A and 16B are views for explaining a concrete method to converta measurement value of the encoder into a position of wafer stage WST;

FIGS. 17A and 17B are views for explaining position measurement of awafer table in an XY plane by an encoder, which is configured of aplurality of heads placed in the shape of an array, and a switchingbetween the heads;

FIGS. 18A to 18E are views for explaining a procedure of an encoderswitching;

FIG. 19 is a view for explaining the switching process of the encoderused in position control of the wafer stage in the XY plane; and

FIG. 20 is a view conceptually showing position control of the waferstage, intake of the measurement value of the encoder, and an encoderswitching timing.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, an embodiment of the present invention will be described,referring to FIGS. 1 to 20.

FIG. 1 shows a schematic configuration of an exposure apparatus 100 inthe embodiment. Exposure apparatus 100 is a projection exposureapparatus of the step-and-scan method, namely the so-called scanner. Asit will be described later, a projection optical system PL is arrangedin the embodiment, and in the description below, a direction parallel toan optical axis AX of projection optical system PL will be described asthe Z-axis direction, a direction within a plane orthogonal to theZ-axis direction in which a reticle and a wafer are relatively scannedwill be described as the Y-axis direction, a direction orthogonal to theZ-axis and the Y-axis will be described as the X-axis direction, androtational (inclination) directions around the X-axis, the Y-axis, andthe Z-axis will be described as θx, θy, and θz directions, respectively.

Exposure apparatus 100 is equipped with an illumination system 10, areticle stage RST that holds a reticle R that is illuminated by anillumination light for exposure (hereinafter, referred to asillumination light, or exposure light) IL from illumination system 10, aprojection unit PU that includes projection optical system PL thatprojects illumination light IL emitted from reticle R on a wafer W, astage device 50 that has a wafer stage WST and a measurement stage MST,their control system, and the like. On wafer stage WST, wafer W ismounted.

Illumination system 10 includes a light source, an illuminanceuniformity optical system, which includes an optical integrator and thelike, and an illumination optical system that has a reticle blind andthe like (none of which are shown), as is disclosed in, for example,Kokai (Japanese Patent Unexamined Application Publication) No.2001-313250 (the corresponding U.S. Patent Application Publication No.2003/0025890) and the like. Illumination system 10 illuminates aslit-shaped illumination area IAR which is set on reticle R with areticle blind (a masking system) by illumination light (exposure light)IL with a substantially uniform illuminance. In this case, asillumination light IL, for example, an ArF excimer laser beam(wavelength 193 nm) is used. Further, as the optical integrator, forexample, a fly-eye lens, a rod integrator (an internal reflection typeintegrator), a diffractive optical element or the like can be used.

On reticle stage RST, reticle R on which a circuit pattern or the likeis formed on its pattern surface (the lower surface in FIG. 1) is fixed,for example, by vacuum chucking. Reticle stage RST is finely drivable ormovable within an XY plane by a reticle stage drive system 11 (not shownin FIG. 1, refer to FIG. 6) that includes a linear motor or the like,and reticle stage RST is also drivable in a scanning direction (in thiscase, the Y-axis direction, which is the lateral direction of the pagesurface in FIG. 1) at a designated scanning speed.

The positional information (including rotation information in the Ozdirection) of reticle stage RST in the XY plane (movement plane) isconstantly detected, for example, at a resolution of around 0.25 nm by areticle laser interferometer (hereinafter referred to as a “reticleinterferometer”) 116, via a movable mirror 15 (the mirrors actuallyarranged are a Y movable mirror (or a retro reflector) that has areflection surface which is orthogonal to the Y-axis direction and an Xmovable mirror that has a reflection surface orthogonal to the X-axisdirection). The measurement values of reticle interferometer 116 aresent to a main controller 20 (not shown in FIG. 1, refer to FIG. 6).Main controller 20 computes the position of reticle stage RST in theX-axis direction, Y-axis direction, and the θz direction based on themeasurement values of reticle interferometer 116, and also controls theposition (and velocity) of reticle stage RST by controlling reticlestage drive system 11 based on the computation results. Incidentally,instead of movable mirror 15, the edge surface of reticle stage RST canbe mirror polished so as to form a reflection surface (corresponding tothe reflection surface of movable mirror 15). Further, reticleinterferometer 116 can measure positional information of reticle stageRST related to at least one of the Z-axis, θx, and θy directions.

Projection unit PU is placed below reticle stage RST in FIG. 1.Projection unit PU includes a barrel 40, and projection optical systemPL that has a plurality of optical elements which are held in apredetermined positional relation inside barrel 40. As projectionoptical system PL, for example, a dioptric system is used, consisting ofa plurality of lenses (lens elements) that is disposed along an opticalaxis AX, which is parallel to the Z-axis direction. Projection opticalsystem PL is, for example, a both-side telecentric dioptric system thathas a predetermined projection magnification (such as one-quarter,one-fifth, or one-eighth times). Therefore, when illumination light ILfrom illumination system 10 illuminates illumination area IAR, a reducedimage of the circuit pattern (a reduced image of a part of the circuitpattern) within illumination area IAR of reticle R is formed, withillumination light IL that has passed through reticle R which is placedso that its pattern surface substantially coincides with a first plane(an object plane) of projection optical system PL, in an area(hereinafter, also referred to as an exposure area) IA conjugate toillumination area IAR on wafer W (exposure area) whose surface is coatedwith a resist (a sensitive agent) and is placed on a second plane (animage plane) side, via projection optical system PL (projection unitPU). And by reticle stage RST and wafer stage WST being synchronouslydriven, the reticle is relatively moved in the scanning direction (theY-axis direction) with respect to illumination area IAR (illuminationlight IL) while wafer W is relatively moved in the scanning direction(the Y-axis direction) with respect to exposure area IA (illuminationlight IL), thus scanning exposure of a shot area (divided area) on waferW is performed, and the pattern of reticle R is transferred onto theshot area. That is, in the embodiment, the pattern is generated on waferW according to illumination system 10, reticle R, and projection opticalsystem PL, and then by the exposure of the sensitive layer (resistlayer) on wafer W with illumination light IL, the pattern is formed onwafer W.

Incidentally, although it is not shown, projection unit PU is installedin a barrel platform supported by three struts via a vibration isolationmechanism. However, as well as such a structure, as is disclosed in, forexample, the pamphlet of International Publication 2006/038952 and thelike, projection unit PU can be supported by suspension with respect toa mainframe member (not shown) placed above projection unit PU or withrespect to a base member on which reticle stage RST is placed.

Incidentally, in exposure apparatus 100 of the embodiment, becauseexposure is performed applying a liquid immersion method, an opening onthe reticle side becomes larger with the substantial increase of thenumerical aperture NA. Therefore, in order to satisfy Petzval'scondition and to avoid an increase in size of the projection opticalsystem, a reflection/refraction system (a catodioptric system) which isconfigured including a mirror and a lens can be employed as a projectionoptical system. Further, in wafer W, in addition to a sensitive layer,for example, a protection film (a topcoat film) which protects the waferor the sensitive layer can also be formed.

Further, in exposure apparatus 100 of the embodiment, in order toperform exposure applying the liquid immersion method, a nozzle unit 32that constitutes part of a local liquid immersion device 8 is arrangedso as to enclose the periphery of the lower end portion of barrel 40that holds an optical element that is closest to an image plane side(wafer W side) that constitutes projection optical system PL, which is alens (hereinafter, also referred to a “tip lens”) 191 in this case. Inthe embodiment, as shown in FIG. 1, the lower end surface of nozzle unit32 is set to be on a substantially flush surface with the lower endsurface of tip lens 191. Further, nozzle unit 32 is equipped with asupply opening and a recovery opening of liquid Lq, a lower surface towhich wafer W is placed facing and at which the recovery opening isarranged, and a supply flow channel and a recovery flow channel that areconnected to a liquid supply pipe 31A and a liquid recovery pipe 31Brespectively. Liquid supply pipe 31A and liquid recovery pipe 31B areslanted by around 45 degrees relative to the X-axis direction and Y-axisdirection in a planar view (when viewed from above) as shown in FIG. 3,and are placed symmetric to a straight line (a reference axis) LV whichpasses through the center (optical axis AX of projection optical systemPL, coinciding with the center of exposure area IA previously describedin the embodiment) of projection unit PU and is also parallel to theY-axis.

One end of a supply pipe (not shown) is connected to liquid supply pipe31A while the other end of the supply pipe is connected to a liquidsupply device 5 (not shown in FIG. 1, refer to FIG. 6), and one end of arecovery pipe (not shown) is connected to liquid recovery pipe 31B whilethe other end of the recovery pipe is connected to a liquid recoverydevice 6 (not shown in FIG. 1, refer to FIG. 6).

Liquid supply device 5 includes a tank for supplying liquid, acompression pump, a temperature controller, a valve for controllingsupply/stop of the liquid to liquid supply pipe 31A, and the like. Asthe valve, for example, a flow rate control valve is preferably used sothat not only the supply/stop of the liquid but also the adjustment offlow rate can be performed. The temperature controller adjusts thetemperature of the liquid within the tank, for example, to nearly thesame temperature as the temperature within the chamber (not shown) wherethe exposure apparatus is housed. Incidentally, the tank, thecompression pump, the temperature controller, the valve, and the like donot all have to be equipped in exposure apparatus 100, and at least partof them can also be substituted by the equipment or the like availablein the plant where exposure apparatus 100 is installed.

Liquid recovery device 6 includes a liquid tank for collecting liquid, asuction pump, a valve for controlling recovery/stop of the liquid vialiquid recovery pipe 31B, and the like. As the valve, it is desirable touse a flow control valve similar to the valve of liquid supply device 5.Incidentally, the tank, the suction pump, the valve, and the like do notall have to be equipped in exposure apparatus 100, and at least part ofthem can also be substituted by the equipment or the like available inthe plant where exposure apparatus 100 is installed.

In the embodiment, as the liquid described above, pure water(hereinafter, it will simply be referred to as “water” besides the casewhen specifying is necessary) that transmits the ArF excimer laser light(light with a wavelength of 193 nm) is to be used. Pure water can beobtained in large quantities at a semiconductor manufacturing plant orthe like without difficulty, and it also has an advantage of having noadverse effect on the photoresist on the wafer, to the optical lenses orthe like.

Refractive index n of the water with respect to the ArF excimer laserlight is around 1.44. In the water the wavelength of illumination lightIL is 193 nm×1/n, shortened to around 134 nm.

Liquid supply device 5 and liquid recovery device 6 each have acontroller, and the respective controllers are controlled by maincontroller 20 (refer to FIG. 6). According to instructions from maincontroller 20, the controller of liquid supply device 5 opens the valveconnected to liquid supply pipe 31A to a predetermined degree to supplyliquid (water) to the space between tip lens 191 and wafer W via liquidsupply pipe 31A, the supply flow channel and the supply opening.Further, when the water is supplied, according to instructions from maincontroller 20, the controller of liquid recovery device 6 opens thevalve connected to liquid recovery pipe 31B to a predetermined degree torecover the liquid (water) from the space between tip lens 191 and waferW into liquid recovery device 6 (the liquid tank) via the recoveryopening, the recovery flow channel and liquid recovery pipe 31B. Duringthe supply and recovery operations, main controller 20 gives commands tothe controllers of liquid supply device 5 and liquid recovery device 6so that the quantity of water supplied to the space between tip lens 191and wafer W constantly equals the quantity of water recovered from thespace. Accordingly, a constant quantity of liquid (water) Lq (refer toFIG. 1) is held in the space between tip lens 191 and wafer W. In thiscase, liquid (water) Lq held in the space between tip lens 191 and waferW is constantly replaced.

As is obvious from the above description, in the embodiment, localliquid immersion device 8 is configured including nozzle unit 32, liquidsupply device 5, liquid recovery device 6, liquid supply pipe 31A andliquid recovery pipe 31B, and the like. Incidentally, part of localliquid immersion device 8, for example, at least nozzle unit 32 may alsobe supported in a suspended state by a main frame (including the barrelplatform described previously) that holds projection unit PU, or mayalso be arranged at another frame member that is separate from the mainframe. Or, in the case projection unit PU is supported in a suspendedstate as is described earlier, nozzle unit 32 may also be supported in asuspended state integrally with projection unit PU, but in theembodiment, nozzle unit 32 is arranged on a measurement frame that issupported in a suspended state independently from projection unit PU. Inthis case, projection unit PU does not have to be supported in asuspended state.

Incidentally, also in the case measurement stage MST is located belowprojection unit PU, the space between a measurement table (to bedescribed later) and tip lens 191 can be filled with water in thesimilar manner to the manner described above.

Incidentally, in the description above, one liquid supply pipe (nozzle)and one liquid recovery pipe (nozzle) were arranged as an example,however, the present invention is not limited to this, and aconfiguration having multiple nozzles as is disclosed in, for example,the pamphlet of International Publication No. 99/49504, may also beemployed, in the case such an arrangement is possible taking intoconsideration a relation with adjacent members. The point is that anyconfiguration can be employed, as long as the liquid can be supplied inthe space between optical member (tip lens) 191 in the lowest endconstituting projection optical system PL and wafer W. For example, theliquid immersion mechanism disclosed in the pamphlet of InternationalPublication No. 2004/053955, or the liquid immersion mechanism disclosedin the EP Patent Application Publication No. 1 420 298 can also beapplied to the exposure apparatus of the embodiment.

Referring back to FIG. 1, stage device 50 is equipped with wafer stageWST and measurement stage MST placed above a base board 12, ameasurement system 200 (refer to FIG. 6) which measures positionalinformation of the stages WST and MST, a stage drive system 124 (referto FIG. 6) which drives both stages WST and MST and the like.Measurement system 200 includes an interferometer system 118 and anencoder system 150, as shown in FIG. 6. Interferometer system 118includes a Y interferometer 16, X interferometers 126, 127, and 128, andZ interferometers 43A and 43B for position measurement of wafer stageWST, and a Y interferometer 18 and an X interferometer 130 for positionmeasurement of measurement stage MST, and the like, as shown in FIG. 2.Incidentally, the configuration and the like of the interferometersystem will be described in detail later on.

Referring back to FIG. 1, on the bottom surface of each of wafer stageWST and measurement stage MST, a noncontact bearing (not shown), forexample, a vacuum preload type hydrostatic air bearing (hereinafter,referred to as an “air pad”) is arranged at a plurality of points, andwafer stage WST and measurement stage MST are supported in a noncontactmanner via a clearance of around several μm above base board 12, bystatic pressure of pressurized air that is blown out from the air padtoward the upper surface of base board 12. Further, both stages WST andMST are independently drivable in the Y-axis direction (a horizontaldirection of the page surface of FIG. 1) and the X-axis direction (anorthogonal direction to the page surface of FIG. 1), by stage drivesystem 124 (refer to FIG. 6) which includes a linear motor and the like.

Wafer stage WST includes a stage main section 91 and a wafer table WTBthat is mounted on stage main section 91. Wafer table WTB and stage mainsection 91 are configured drivable in directions of six degrees offreedom (X, Y, Z, θx, θy, and θz) with respect to base board 12 by adrive system including a linear motor and a Z leveling mechanism (e.g.,including a voice coil motor and the like).

On wafer table WTB, a wafer holder (not shown) that holds wafer W byvacuum suction or the like is arranged. The wafer holder may also beformed integrally with wafer table WTB, but in the embodiment, the waferholder and wafer table WTB are separately configured, and the waferholder is fixed inside a recessed portion of wafer table WTB, forexample, by vacuum suction or the like. Further, on the upper surface ofwafer table WTB, a plate (liquid repellent plate) 28 is arranged, whichhas a surface (liquid repellent surface) on a substantially flushsurface with the surface of wafer W mounted on the wafer holder to whichliquid repellent processing with respect to liquid Lq is performed, hasa rectangular outer shape (contour), and also has a circular openingslightly larger than the wafer holder (a mounting area of the wafer)which is formed in the center portion. Plate 28 is made of materialswith a low coefficient of thermal expansion, such as glass or ceramics(e.g., such as Zerodur (the brand name) of Schott AG, Al₂O₃, or TiC),and on the surface of plate 28, a liquid repellent film is formed by,for example, fluorine resin materials, fluorine series resin materialssuch as polytetrafluoroethylene (Teflon (registered trademark)), acrylicresin materials, or silicon series resin materials. Further, as shown ina planar view of wafer table WTB (wafer stage WST) in FIG. 4A, plate 28has a first liquid repellent area 28 a whose outer shape (contour) isrectangular enclosing a circular opening, and a second liquid repellentarea 28 b that has a rectangular frame (annular) shape placed around thefirst liquid repellent area 28 a. On first liquid repellent area 28 a,for example, at the time of an exposure operation, at least part of aliquid immersion area 14 (refer to FIG. 8) that is protruded from thesurface of the wafer is formed, and on second liquid repellent area 28b, scales for an encoder system (to be described later) are formed.Incidentally, at least part of the surface of plate 28 does not have tobe on a flush surface with the surface of the wafer, that is, may have adifferent height from that of the surface of the wafer. Further, plate28 may be a single plate, but in the embodiment, plate 28 is configuredby combining a plurality of plates, for example, the first and secondliquid repellent plates that correspond to the first liquid repellentarea 28 a and the second liquid repellent area 28 b respectively. In theembodiment, water is used as liquid Lq as is described above, andtherefore, hereinafter the first liquid repellent area 28 a and thesecond liquid repellent area 28 b are also referred to as a first waterrepellent plate 28 a and a second water repellent plate 28 b.

In this case, exposure light IL is irradiated to the first waterrepellent plate 28 a on the inner side, while exposure light IL ishardly irradiated to the second water repellent plate 28 b on the outerside. Taking this fact into consideration, in the embodiment, a firstliquid repellent area to which water repellent coat having sufficientresistance to exposure light IL (light in a vacuum ultraviolet region,in this case) is applied is formed on the surface of the first waterrepellent plate 28 a, and a second liquid repellent area to which waterrepellent coat having resistance to exposure light IL inferior to thefirst liquid repellent area is applied is formed on the surface of thesecond water repellent plate 28 b. In general, since it is difficult toapply water repellent coat having sufficient resistance to exposurelight IL (in this case, light in a vacuum ultraviolet region) to a glassplate, it is effective to separate the water repellent plate into twosections, the first water repellent plate 28 a and the second waterrepellent plate 28 b which is the periphery of the first water repellentplate, in the manner described above. Incidentally, the presentinvention is not limited to this, and two types of water repellent coatthat have different resistance to exposure light IL may also be appliedon the upper surface of the same plate in order to form the first liquidrepellent area and the second liquid repellent area. Further, the samekind of water repellent coat may be applied to the first and secondliquid repellent areas. For example, only one liquid repellent area mayalso be formed on the same plate.

Further, as is obvious from FIG. 4A, at the end portion on the +Y sideof the first water repellent plate 28 a, a rectangular cutout is formedin the center portion in the X-axis direction, and a measurement plate30 is embedded inside the rectangular space (inside the cutout) that isenclosed by the cutout and the second water repellent plate 28 b. Afiducial mark FM is formed in the center in the longitudinal directionof measurement plate 30 (on a centerline LL of wafer table WTB), and apair of aerial image measurement slit patterns (slit-shaped measurementpatterns) SL are formed in the symmetrical placement with respect to thecenter of fiducial mark FM on one side and the other side in the X-axisdirection of fiducial mark FM. As each of aerial image measurement slitpatterns SL, an L-shaped slit pattern having sides along the Y-axisdirection and X-axis direction, or two linear slit patterns extending inthe X-axis and Y-axis directions respectively can be used, as anexample.

Further, as is shown in FIG. 4B, inside wafer stage WST below each ofaerial image measurement slit patterns SL, an L-shaped housing 36 inwhich an optical system containing an objective lens, a mirror, a relaylens and the like is housed is attached in a partially embedded statepenetrating through part of the inside of wafer table WTB and stage mainsection 91. Housing 36 is arranged in pairs corresponding to the pair ofaerial image measurement slit patterns SL, although omitted in thedrawing.

The optical system inside housing 36 guides illumination light IL thathas been transmitted through aerial image measurement slit pattern SLalong an L-shaped route and emits the light toward a −Y direction.Incidentally, in the following description, the optical system insidehousing 36 is described as a light-transmitting system 36 by using thesame reference code as housing 36 for the sake of convenience.

Moreover, on the upper surface of the second water repellent plate 28 b,multiple grid lines are directly formed in a predetermined pitch alongeach of four sides. More specifically, in areas on one side and theother side in the X-axis direction of second water repellent plate 28 b(both sides in the horizontal direction in FIG. 4A), Y scales 39Y₁ and39Y₂ are formed respectively, and Y scales 39Y₁ and 39Y₂ are eachcomposed of a reflective grating (for example, a diffraction grating)having a periodic direction in the Y-axis direction in which grid lines38 having the longitudinal direction in the X-axis direction are formedin a predetermined pitch along a direction parallel to the Y-axis (theY-axis direction).

Similarly, in areas on one side and the other side in the Y-axisdirection of second water repellent plate 28 b (both sides in thevertical direction in FIG. 4A), X scales 39X₁ and 39X₂ are formedrespectively in a state where the scales are placed between Y scales39Y₁ and 39Y₂, and X scales 39X₁ and 39X₂ are each composed of areflective grating (for example, a diffraction grating) having aperiodic direction in the X-axis direction in which grid lines 37 havingthe longitudinal direction in the Y-axis direction are formed in apredetermined pitch along a direction parallel to the X-axis (the X-axisdirection). As each of the scales, the scale made up of a reflectivediffraction grating RG (refer to FIG. 7A) that is created by, forexample, hologram or the like on the surface of the second waterrepellent plate 28 b is used. In this case, each scale has gratings madeup of narrow slits, grooves or the like that are marked at apredetermined distance (pitch) as graduations. The type of diffractiongrating used for each scale is not limited, and not only the diffractiongrating made up of grooves or the like that are mechanically formed, butalso, for example, the diffraction grating that is created by exposinginterference fringe on a photosensitive resin may be used. However, eachscale is created by marking the graduations of the diffraction grating,for example, in a pitch between 138 nm to 4 μm, for example, a pitch of1 μm on a thin plate shaped glass. These scales are covered with theliquid repellent film (water repellent film) described above.Incidentally, the pitch of the grating is shown much wider in FIG. 4Athan the actual pitch, for the sake of convenience. The same is truealso in other drawings.

In this manner, in the embodiment, since the second water repellentplate 28 b itself constitutes the scales, a glass plate with a lowcoefficient of thermal expansion is to be used as the second waterrepellent plate 28 b. However, the present invention is not limited tothis, and a scale member made up of a glass plate or the like with a lowcoefficient of thermal expansion on which a grating is formed may alsobe fixed on the upper surface of wafer table WTB, for example, by aplate spring (or vacuum suction) or the like so as to prevent localshrinkage/expansion. In this case, a water repellent plate to which thesame water repellent coat is applied on the entire surface may be usedinstead of plate 28. Or, wafer table WTB may also be formed by materialswith a low coefficient of thermal expansion, and in such a case, a pairof Y scales and a pair of X scales may be directly formed on the uppersurface of wafer table WTB.

Incidentally, in order to protect the diffraction grating, it is alsoeffective to cover the grating with a glass plate with a low coefficientof thermal expansion that has water repellency (liquid repellency). Inthis case, as the glass plate, a plate whose thickness is the same levelas the wafer, such as for example, a plate 1 mm thick, can be used, andthe plate is set on the upper surface of wafer table WST so that thesurface of the glass plate becomes the same height (a flush surface) asthe wafer surface.

Incidentally, a layout pattern is arranged for deciding the relativeposition between an encoder head and a scale near the edge of each scale(to be described later). The layout pattern is configured, for example,from grid lines that have different reflectivity, and when the encoderhead scans the layout pattern, the intensity of the output signal of theencoder changes. Therefore, a threshold value is determined beforehand,and the position where the intensity of the output signal exceeds thethreshold value is detected. Then, the relative position between theencoder head and the scale is set, with the detected position as areference.

Measurement stage MST includes stage main section 92, and measurementtable MTB mounted on stage main section 92. Measurement stage MST isconfigured drivable in directions of six degrees of freedom (X, Y, Z,θx, θy, and θz) with respect to base board 12 by a drive system (notshown), similar to wafer stage WST. However, the present invention isnot limited to this, and for example, measurement stage MST can employthe so-called coarse and fine movement structure in which measurementtable MTB can be finely driven in the X-axis direction, the Y-axisdirection, and the θz direction with respect to stage main section 92,or measurement table MTB can be configured drivable in directions ofthree degrees of freedom, which are Z, θx, and θy, on stage main section92.

Incidentally, the drive system of wafer stage WST and the drive systemof measurement stage MST are included in FIG. 6, and are shown as stagedrive system 124.

Various measurement members are arranged at measurement table MTB (andstage main section 92). As such measurement members, for example, asshown in FIGS. 2 and 5A, members such as an uneven illuminance measuringsensor 94 that has a pinhole-shaped light-receiving section whichreceives illumination light IL on an image plane of projection opticalsystem PL, an aerial image measuring instrument 96 that measures anaerial image (projected image) of a pattern projected by projectionoptical system PL, a wavefront aberration measuring instrument 98 by theShack-Hartman method that is disclosed in, for example, the pamphlet ofInternational Publication No. 03/065428 and the like are employed. Aswavefront aberration measuring instrument 98, the one disclosed in, forexample, the pamphlet of International Publication No. 99/60361 (thecorresponding EP Patent Application No. 1 079 223) can also be used.

As uneven illuminance measuring sensor 94, the configuration similar tothe one that is disclosed in, for example, Kokai (Japanese UnexaminedPatent Application Publication) No. 57-117238 (the corresponding U.S.Pat. No. 4,465,368) and the like can be used. Further, as aerial imagemeasuring instrument 96, the configuration similar to the one that isdisclosed in, for example, Kokai (Japanese Unexamined Patent ApplicationPublication) No. 2002-014005 (the corresponding U.S. Patent ApplicationPublication No. 2002/0041377) and the like can be used. Incidentally, inthe embodiment, three measurement members (94, 96 and 98) were to bearranged at measurement stage MST, however, the type of the measurementmember and/or the number is not limited to them. As the measurementmembers, for example, measurement members such as a transmittancemeasuring instrument that measures a transmittance of projection opticalsystem PL, and/or a measuring instrument that observes local liquidimmersion device 8, for example, nozzle unit 32 (or tip lens 191) or thelike may also be used. Furthermore, members different from themeasurement members such as a cleaning member that cleans nozzle unit32, tip lens 191 or the like may also be mounted on measurement stageMST.

In the embodiment, as can be seen from FIG. 5A, the sensors that arefrequently used such as uneven illuminance measuring sensor 94 andaerial image measuring instrument 96 are placed on a centerline CL(Y-axis passing through the center) of measurement stage MST. Therefore,in the embodiment, measurement using these sensors can be performed bymoving measurement stage MST only in the Y-axis direction without movingthe measurement stage in the X-axis direction.

In addition to each of the sensors described above, an illuminancemonitor that has a light-receiving section having a predetermined areasize that receives illumination light IL on the image plane ofprojection optical system PL may also be employed, which is disclosedin, for example, Kokai (Japanese Unexamined Patent ApplicationPublication) No. 11-016816 (the corresponding U.S. Patent ApplicationPublication No. 2002/0061469) and the like. The illuminance monitor isalso preferably placed on the centerline.

Incidentally, in the embodiment, liquid immersion exposure is performedin which wafer W is exposed with exposure light (illumination light) ILvia projection optical system PL and liquid (water) Lq, and accordinglyuneven illuminance measuring sensor 94 (and the illuminance monitor),aerial image measuring instrument 96 and wavefront aberration measuringinstrument 98 that are used in measurement using illumination light ILreceive illumination light IL via projection optical system PL andwater. Further, only part of each sensor such as the optical system maybe mounted on measurement table MTB (and stage main section 92), or theentire sensor may be placed on measurement table MTB (and stage mainsection 92).

As shown in FIG. 5B, a frame-shaped attachment member 42 is fixed to theend surface on the −Y side of stage main section 92 of measurement stageMST. Further, to the end surface on the −Y side of stage main section92, a pair of photodetection systems 44 are fixed in the vicinity of thecenter position in the X-axis direction inside an opening of attachmentmember 42, in the placement capable of facing a pair oflight-transmitting systems 36 described previously. Each ofphotodetection systems 44 is composed of an optical system such as arelay lens, a light receiving element such as a photomultiplier tube,and a housing that houses them. As is obvious from FIGS. 4B and 5B andthe description so far, in the embodiment, in a state where wafer stageWST and measurement stage MST are closer together within a predetermineddistance in the Y-axis direction (including a contact state),illumination light IL that has been transmitted through each aerialimage measurement slit pattern SL of measurement plate 30 is guided byeach light-transmitting system 36 and received by the light-receivingelement of each photodetection system 44. That is, measurement plate 30,light-transmitting systems 36 and photodetection systems 44 constitutean aerial image measuring device 45 (refer to FIG. 6), which is similarto the one disclosed in Kokai (Japanese Unexamined Patent ApplicationPublication) No. 2002-014005 (the corresponding U.S. Patent ApplicationPublication No. 2002/0041377) referred to previously, and the like.

On attachment member 42, a fiducial bar (hereinafter, shortly referredto as an “FD bar”) which is made up of a bar-shaped member having arectangular sectional shape is arranged extending in the X-axisdirection. FD bar 46 is kinematically supported on measurement stage MSTby a full-kinematic mount structure.

Since FD bar 46 serves as a prototype standard (measurement standard),optical glass ceramics with a low coefficient of thermal expansion, suchas Zerodur (the brand name) of Schott AG are employed as the materials.The flatness degree of the upper surface (the surface) of FD bar 46 isset high to be around the same level as a so-called datum plane plate.Further, as shown in FIG. 5A, a reference grating (for example, adiffraction grating) 52 whose periodic direction is in the Y-axisdirection is respectively formed in the vicinity of the end portions onone side and the other side in the longitudinal direction of FD bar 46.The pair of reference gratings 52 is formed placed apart from each otherat a predetermined distance L, symmetric to the center in the X-axisdirection of FD bar 46, or more specifically, formed in a symmetricplacement to centerline CL previously described.

Further, on the upper surface of FD bar 46, a plurality of referencemarks M are formed in a placement as shown in FIG. 5A. The plurality ofreference marks M are formed in three-row arrays in the Y-axis directionin the same pitch, and the array of each row is formed being shiftedfrom each other by a predetermined distance in the X-axis direction. Aseach of reference marks M, a two-dimensional mark having a size that canbe detected by a primary alignment system and secondary alignmentsystems (to be described later) is used. Reference mark M may also bedifferent in shape (constitution) from fiducial mark FM, but in theembodiment, reference mark M and fiducial mark FM have the sameconstitution and also they have the same constitution with that of analignment mark of wafer W. Incidentally, in the embodiment, the surfaceof FD bar 46 and the surface of measurement table MTB (which may includethe measurement members described above) are also covered with a liquidrepellent film (water repellent film) severally.

In exposure apparatus 100 of the embodiment, although it is omitted inFIG. 1 from the viewpoint of avoiding intricacy of the drawing, as shownin FIG. 3, a primary alignment system AL1 having a detection center at aposition spaced apart from optical axis AX of the projection opticalsystem at a predetermined distance on the −Y side is actually placed onreference axis LV. Primary alignment system AL1 is fixed to the lowersurface of a main frame (not shown) via a support member 54. On one sideand the other side in the X-axis direction with primary alignment systemAL1 in between, secondary alignment systems AL2 ₁ and AL2 ₂, and AL2 ₃and AL2 ₄ whose detection centers are substantially symmetrically placedwith respect to straight line LV are severally arranged. That is, fivealignment systems AL₁ and AL2 ₁ to AL2 ₄ are placed so that theirdetection centers are placed at different positions in the X-axisdirection, that is, placed along the X-axis direction.

As is representatively shown by secondary alignment system AL2 ₄, eachsecondary alignment system AL2 _(n) (n=1 to 4) is fixed to a tip(turning end) of an arm 56 _(n) (n=1 to 4) that can turn around arotation center O as the center in a predetermined angle range inclockwise and anticlockwise directions in FIG. 3. In the embodiment, apart of each secondary alignment system AL2 _(n) (e.g. including atleast an optical system that irradiates an alignment light to adetection area and also leads the light that is generated from a subjectmark within the detection area to a light-receiving element) is fixed toarm 56 _(n) and the remaining section is arranged at the main frame thatholds projection unit PU. The X-positions of secondary alignment systemsAL2 ₁ to AL2 ₄ are severally adjusted by rotating around rotation centerO as the center. In other words, the detection areas (or the detectioncenters) of secondary alignment systems AL2 ₁ to AL2 ₄ are independentlymovable in the X-axis direction. Accordingly, the relative positions ofthe detection areas of primary alignment system AL1 and secondaryalignment systems AL2 ₁ to AL2 ₄ are adjustable in the X-axis direction.Incidentally, in the embodiment, the X-positions of secondary alignmentsystems AL2 ₁ to AL2 ₄ are to be adjusted by the rotation of the arms.However, the present invention is not limited to this, and a drivemechanism that drives secondary alignment systems AL2 ₁ to AL2 ₄ backand forth in the X-axis direction may also be arranged. Further, atleast one of secondary alignment systems AL2 ₁ to AL2 ₄ can be moved notonly in the X-axis direction but also in the Y-axis direction.Incidentally, since part of each secondary alignment system AL2 _(n) ismoved by arm 56 _(n), positional information of the part that is fixedto arm 56 _(n) is measurable by a sensor (not shown) such as, forexample, an interferometer or an encoder. The sensor may only measurepositional information in the X-axis direction of secondary alignmentsystem AL2 _(n), or may be capable of measuring positional informationin another direction, for example, the Y-axis direction and/or therotational direction (including at least one of the θx and θydirections).

On the upper surface of each arm 56 _(n), a vacuum pad 58 _(n) (n=1 to4, not shown in FIG. 3, refer to FIG. 6) that is composed of adifferential evacuation type air bearing is arranged. Further, arm 56_(n) can be turned by a rotation drive mechanism 60 _(n) (n=1 to 4, notshown in FIG. 3, refer to FIG. 6) that includes, for example, a motor orthe like, in response to instructions of main controller 20. Maincontroller 20 activates each vacuum pad 58 _(n) to fix each arm 56 _(n)to a main frame (not shown) by suction after rotation adjustment of arm56 _(n). Thus, the state of each arm 56 _(n) after rotation angleadjustment, that is, a desired positional relation between primaryalignment system AL1 and four secondary alignment systems AL2 ₁ to AL2 ₄is maintained.

Incidentally, in the case a portion of the main frame facing arm 56 _(n)is a magnetic body, an electromagnet may also be employed instead ofvacuum pad 58.

In the embodiment, as each of primary alignment system AL1 and foursecondary alignment systems AL2 ₁ to AL2 ₄, for example, an FIA (FieldImage Alignment) system by an image processing method is used thatirradiates a broadband detection beam that does not expose resist on awafer to a subject mark, and picks up an image of the subject markformed on a light-receiving plane by the reflected light from thesubject mark and an image of an index (an index pattern on an indexplate arranged within each alignment system) (not shown), using animaging device (such as CCD), and then outputs their imaging signals.The imaging signal from each of primary alignment system AL1 and foursecondary alignment systems AL2 ₁ to AL2 ₄ is supplied to maincontroller 20 in FIG. 6, via an alignment signal processing system (notshown).

Incidentally, each of the alignment systems described above is notlimited to the FIA system, and an alignment sensor, which irradiates acoherent detection light to a subject mark and detects a scattered lightor a diffracted light generated from the subject mark or makes twodiffracted lights (e.g. diffracted lights of the same order ordiffracted lights being diffracted in the same direction) generated fromthe subject mark interfere and detects an interference light, cannaturally be used alone or in combination as needed. Further, in theembodiment, five alignment systems AL1 and AL2 ₁ to AL2 ₄ are to befixed to the lower surface of the main frame that holds projection unitPU, via support member 54 or arm 56 _(n). However, the present inventionis not limited to this, and for example, the five alignment systems mayalso be arranged on the measurement frame described earlier.

Next, a configuration and the like of interferometer system 118 whichmeasures the positional information of wafer stage WST and measurementstage MST will be described.

To the −Y edge surface and the −X edge surface of wafer table WTB,mirror-polishing is applied, respectively, and a reflection surface 17 aand a reflection surface 17 b shown in FIG. 2 are formed. By severallyprojecting a measurement beam to reflection surface 17 a and reflectionsurface 17 b and receiving a reflected light of each beam, Yinterferometer 16 and X interferometers 126, 127, and 128 (Xinterferometers 126 to 128 are not shown in FIG. 1, refer to FIG. 2)constituting a part of interferometer system 118 (refer to FIG. 6)measure a displacement of each reflection surface from a datum position(for example, a fixed mirror is placed on the side surface of projectionunit PU, and the surface is used as a reference surface), that is,positional information of wafer stage WST within the XY plane, and themeasured positional information is supplied to main controller 20. Inthe embodiment, as it will be described later on, as each interferometera multiaxial interferometer that has a plurality of measurement axes isused with an exception for a part of the interferometers.

Meanwhile, to the side surface on the −Y side of stage main section 91,a movable mirror 41 having the longitudinal direction in the X-axisdirection is attached via a kinematic support mechanism (not shown), asshown in FIGS. 4A and 4B. Movable mirror 41 is made of a member which islike a rectangular solid member integrated with a pair of triangularprisms adhered to a surface (the surface on the −Y side) of therectangular solid member. As it can be seen from FIG. 2, movable mirror41 is designed so that the length in the X-axis direction is longer thanreflection surface 17 a of wafer table WTB by at least the spacingbetween the two Z interferometers which will be described later.

To the surface on the −Y side of movable mirror 41, mirror-polishing isapplied, and three reflection surfaces 41 b, 41 a, and 41 c are formed,as shown in FIG. 4B. Reflection surface 41 a configures a part of theedge surface on the −Y side of movable mirror 41, and reflection surface41 a is parallel with the XZ plane and also extends in the X-axisdirection. Reflection surface 41 b configures a surface adjacent toreflection surface 41 a on the +Z side, forming an obtuse angle toreflection surface 41 a, and spreading in the X-axis direction.Reflection surface 41 c configures a surface adjacent to the −Z side ofreflection surface 41 a, and is arranged symmetrically with reflectionsurface 41 b, with reflection surface 41 b in between.

A pair of Z interferometers 43A and 43B (refer to FIGS. 1 and 2) thatconfigures a part of interferometer system 118 (refer to FIG. 6) andirradiates measurement beams on movable mirror 41 is arranged facingmovable mirror 41.

As it can be seen when viewing FIGS. 1 and 2 together, Z interferometers43A and 43B are placed apart on one side and the other side of Yinterferometer 16 in the X-axis direction at a substantially equaldistance and at positions slightly lower than Y interferometer 16,respectively.

From each of the Z interferometers 43A and 43B, as shown in FIG. 1,measurement beam B1 along the Y-axis direction is projected towardreflection surface 41 b, and measurement beam B2 along the Y-axisdirection is projected toward reflection surface 41 c (refer to FIG.4B). In the embodiment, fixed mirror 47B having a reflection surfaceorthogonal to measurement beam B1 sequentially reflected off reflectionsurface 41 b and reflection surface 41 c and a fixed mirror 47A having areflection surface orthogonal to measurement beam B2 sequentiallyreflected off reflection surface 41 c and reflection surface 41 b arearranged, each extending in the X-axis direction at a position distancedapart from movable mirror 41 in the −Y direction by a predetermineddistance in a state where the fixed mirrors do not interfere withmeasurement beams B1 and B2.

Fixed mirrors 47A and 47B are supported, for example, by the samesupport body (not shown) arranged in the frame (not shown) whichsupports projection unit PU.

Y interferometer 16, as shown in FIG. 8 (and FIG. 2), projectsmeasurement beams B4 ₁ and B4 ₂ on reflection surface 17 a of wafertable WTB along a measurement axis in the Y-axis direction spaced apartby an equal distance to the −X side and the +X side from reference axisLV previously described, and by receiving each reflected light, detectsthe position of wafer table WTB in the Y-axis direction (a Y position)at the irradiation point of measurement beams B4 ₁ and B4 ₂.Incidentally, in FIG. 1, measurement beams B4 ₁ and B4 ₂ arerepresentatively shown as measurement beam B4.

Further, Y interferometer 16 projects a measurement beam B3 towardreflection surface 41 a along measurement axes in the Y-axis directionwith a predetermined distance in the Z-axis direction spaced betweenmeasurement beams B4 ₁ and B4 ₂, and by receiving measurement beam B3reflected off reflection surface 41 a, detects the Y position ofreflection surface 41 a (more specifically wafer stage WST) of movablemirror 41.

Main controller 20 computes the Y position (or to be more precise,displacement ΔY in the Y-axis direction) of reflection surface 17 a, ormore specifically, wafer table WTB (wafer stage WST), based on anaverage value of the measurement values of the measurement axescorresponding to measurement beams B4 ₁ and B4 ₂ of Y interferometer 16.Further, main controller 20 computes displacement (yawing amount)Δθz^((Y)) in the rotational direction around the Z-axis (the θzdirection) of wafer table WTB, based on a difference of the measurementvalues of the measurement axes corresponding to measurement beams B4 ₁and B4 ₂. Further, main controller 20 computes displacement (pitchingamount) Δθx in the θx direction of wafer stage WST, based on the Yposition (displacement ΔY in the Y-axis direction) of reflection surface17 a and reflection surface 41 a.

Further, as shown in FIGS. 8 and 2, X interferometer 126 projectsmeasurement beams B5 ₁ and B5 ₂ on wafer table WTB along the dualmeasurement axes spaced apart from a straight line (a reference axis) LHin the X-axis direction that passes the optical axis of projectionoptical system PL by the same distance. And, based on the measurementvalues of the measurement axes corresponding to measurement beams B5 ₁and B5 ₂, main controller 20 computes a position in the X-axis direction(an X position, or to be more precise, displacement ΔX in the X-axisdirection) of wafer table WTB. Further, main controller 20 computesdisplacement (yawing amount) Δθz^((X)) of wafer table WTB in the θzdirection from a difference of the measurement values of the measurementaxes corresponding to measurement beams B5 ₁ and B5 ₂. Incidentally,Δθz^((X)) obtained from X interferometer 126 and Δθz^((Y)) obtained fromY interferometer 16 are equal to each other, and represents displacement(yawing amount) Δθz of wafer table WTB in the θz direction.

Further, as shown in the drawings such as FIGS. 9 and 10, a measurementbeam B7 from X interferometer 128 is projected on reflection surface 17b of wafer table WTB along a straight line LUL, which is a lineconnecting an unloading position UP where unloading of the wafer onwafer table WTB is performed and a loading position LP where loading ofthe wafer onto wafer table WTB is performed and is parallel to theX-axis. Further, as shown in the drawings such as FIGS. 11 and 12, ameasurement beam B6 from X interferometer 127 is projected on reflectionsurface 17 b of wafer table WTB along a straight line (a reference axis)LA, which passes through the detection center of primary alignmentsystem AL1 and is parallel to the X-axis.

Main controller 20 can obtain displacement ΔX of wafer table WTB in theX-axis direction from the measurement values of X interferometer 127 andthe measurement values of X interferometer 128. However, the three Xinterferometers 126, 127, and 128 are placed differently regarding theY-axis direction, and X interferometer 126 is used at the time ofexposure as shown in FIG. 8, X interferometer 127 is used at the time ofwafer alignment as shown in FIG. 12, and X interferometer 128 is used atthe time of wafer unloading shown in FIG. 9 and wafer loading shown inFIG. 10.

From Z interferometers 43A and 43B previously described, measurementbeams B1 and B2 that proceed along the Y-axis are projected towardmovable mirror 41, respectively, as shown in FIG. 1. These measurementbeams B1 and B2 are incident on reflection surfaces 41 b and 41 c ofmovable mirror 41, respectively, at a predetermined angle of incidence(the angle is to be θ/2). Then, measurement beam B1 is sequentiallyreflected by reflection surfaces 41 b and 41 c, and then is incidentperpendicularly on the reflection surface of fixed mirror 47B, whereasmeasurement beam B2 is sequentially reflected by reflection surfaces 41c and 41 b and is incident perpendicularly on the reflection surface offixed mirror 47A. Then, measurement beams B2 and B1 reflected off thereflection surface of fixed mirrors 47A and 47B are sequentiallyreflected by reflection surfaces 41 b and 41 c again, or aresequentially reflected by reflection surfaces 41 c and 41 b again(returning the optical path at the time of incidence oppositely), andthen are received by Z interferometers 43A and 43B.

In this case, when displacement of movable mirror 41 (more specifically,wafer stage WST) in the Z-axis direction is ΔZo and displacement in theY-axis direction is ΔYo, an optical path length change AL1 ofmeasurement beam B1 and an optical path length change ΔL2 of measurementbeam B2 can respectively be expressed as in formulas (1) and (2) below.

ΔL1=ΔYo×(1+cos θ)+ΔZo×sin θ  (1)

ΔL2=ΔYo×(1+cos θ)−ΔZo×sin θ  (2)

Accordingly, from formulas (1) and (2), ΔZo and ΔYo can be obtainedusing the following formulas (3) and (4).

ΔZo=(ΔL1−ΔL2)/2 sin θ  (3)

ΔYo=(ΔL1+ΔL2)/{2(1+cos θ)}  (4)

Displacements ΔZo and ΔYo above can be obtained with Z interferometers43A and 43B. Therefore, displacement which is obtained using Zinterferometer 43A is to be ΔZoR and ΔYoR, and displacement which isobtained using Z interferometer 43B is to be ΔZoL and ΔYoL. And thedistance between measurement beams B1 and B2 projected by Zinterferometers 43A and 43B, respectively, in the X-axis direction is tobe a distance D (refer to FIG. 2). Under such premises, displacement(yawing amount) Δθz of movable mirror 41 (more specifically, wafer stageWST) in the θz direction and displacement (rolling amount) Δθy in the θydirection can be obtained by the following formulas (5) and (6).

Δθz=tan⁻¹{(ΔYoR−ΔYoL)/D}  (5)

Δθy=tan⁻¹{(ΔZoL−ΔZoR)/D}  (6)

Accordingly, by using the formulas (3) to (6) above, main controller 20can compute displacement of wafer stage WST in four degrees of freedom,ΔZo, ΔYo, Δθz, and Δθy, based on the measurement results of Zinterferometers 43A and 43B.

In the manner described above, from the measurement results ofinterferometer system 118, main controller 20 can obtain displacement ofwafer stage WST in directions of six degrees of freedom (Z, X, Y, θz,θx, and θy directions).

Incidentally, in the embodiment, the case has been described where waferstage WST is configured of a single stage that can move in six degreesof freedom which includes stage main section 91 and wafer table WTBmounted on stage main section 91, however, the present invention is notlimited to this, and wafer stage WST can be configured including stagemain section 91 which can move freely in the XY plane, and wafer tableWTB that can be finely driven relative to the stage main section atleast in the Z-axis direction, the θx direction, and the θy direction.Further, instead of reflection surface 17 a and reflection surface 17 b,a movable mirror consisting of a plane mirror can be arranged in wafertable WTB. Furthermore, positional information of wafer stage WST was tobe measured with a reflection surface of a fixed mirror arranged inprojection unit PU serving as a reference surface, however, the positionto place the reference surface at is not limited to projection unit PU,and the fixed mirror does not always have to be used to measure thepositional information of wafer stage WST.

In the embodiment, however, position information within the XY plane(including the rotation information in the θz direction) of wafer stageWST (wafer table WTB) is mainly measured by an encoder system (to bedescribed later), and the measurement values of interferometers 16, 126,and 127 are secondarily used in cases such as when long-term fluctuation(for example, by temporal deformation or the like of the scales) of themeasurement values of the encoder system is corrected (calibrated).

Incidentally, at least part of interferometer system 118 (such as anoptical system) may be arranged at the main frame that holds projectionunit PU, or may also be arranged integrally with projection unit PU thatis supported in a suspended state as is described above, however, in theembodiment, interferometer system 118 is to be arranged at themeasurement frame described above.

Further, in the embodiment, positional information of wafer stage WSTmeasured by interferometer system 118 is not used in operations such asthe exposure operation and the alignment operation which will bedescribed later on, and was mainly to be used in calibration operations(more specifically, calibration of measurement values) of the encodersystem, however, the measurement information (more specifically, atleast one of the positional information in directions of six degrees offreedom) of interferometer system 118 can be used in operations such asthe exposure operation and/or the alignment operation. In theembodiment, the encoder system measures positional information of waferstage WST in directions of three degrees of freedom, or morespecifically, the X-axis, the Y-axis, and the θz directions. Therefore,in the exposure operation and the like, of the measurement informationof interferometer system 118, positional information related to adirection that is different from the measurement direction (the X-axis,the Y-axis, and the Oz direction) of wafer stage WST by the encodersystem, such as, for example, only the positional information related toat least one direction among the Z-axis direction, the θx direction, andthe θy direction can be used, or in addition to the positionalinformation in the different direction, positional information relatedto the same direction (more specifically, at least one of the X-axis,the Y-axis, and the θz directions) as the measurement direction of theencoder system can also be used. Further, in the exposure operation andthe like, the positional information of wafer stage WST in the Z-axisdirection measured using interferometer system 118 can be used.

In addition, interferometer system 118 (refer to FIG. 6) includes a Yinterferometer 18 and an X interferometer 130 for measuring thetwo-dimensional position coordinates of measurement table MTB. Also onthe +Y end surface and the −X end surface of measurement table MTB,reflection surfaces 19 a and 19 b are formed similar to wafer table WTBas is described above (refer to FIGS. 2 and 5A). Y interferometer 18 andX interferometer 130 (X interferometer 130 is not shown in FIG. 1, referto FIG. 2) of interferometer system 118 project measurement beams onreflection surfaces 19 a and 19 b as shown in FIG. 2, and measure thedisplacement from a reference position of each reflection surface byreceiving the respective reflected lights. Main controller 20 receivesthe measurement values of Y interferometer 18 and X interferometer 130,and computes the positional information (for example, including at leastthe positional information in the X-axis and the Y-axis directions androtation information in the θz direction) of measurement stage MST.

Incidentally, as the Y interferometer used for measuring measurementtable MTB, a multiaxial interferometer which is similar to Yinterferometer 16 used for measuring wafer table WTB can be used.Further, as the X interferometer used for measuring measurement tableMTB, a two-axis interferometer which is similar to X interferometer 126used for measuring wafer table WTB can be used. Further, in order tomeasure Z displacement, Y displacement, yawing amount, and rollingamount of measurement stage MST, interferometers similar to Zinterferometers 43A and 43B used for measuring wafer table WTB can beintroduced.

Next, the structure and the like of the encoder system which measurespositional information (including rotation information in the θzdirection) of wafer table WTB in the XY plane will be described.

In exposure apparatus 100 of the embodiment, as shown in FIG. 3, fourhead units 62A to 62D of the encoder system are placed in a state ofsurrounding nozzle unit 32 on all four sides. In actual practice, headunits 62A to 62D are fixed to the foregoing main frame that holdsprojection unit PU in a suspended state via a support member, althoughomitted in the drawings such as FIG. 3 from the viewpoint of avoidingintricacy of the drawings.

As shown in FIG. 3, head units 62A and 62C are placed on the +X side andthe −X side of projection unit PU, with the X-axis direction serving asa longitudinal direction. Head units 62A and 62C are respectivelyequipped with a plurality of (five, in this case) Y heads 65 ₁ to 65 ₅and 64 ₁ to 64 ₅ that are placed at a distance WD in the X-axisdirection. More particularly, head units 62A and 62C are each equippedwith a plurality of (four, in this case) Y heads (64 ₁ to 64 ₄ or 65 ₂to 65 ₅) that are placed on straight line (reference axis) LH whichpasses through optical axis AX of projection optical system PL and isalso parallel to the X-axis at distance WD except for the periphery ofprojection unit PU, and a Y head (64 ₅ or 65 ₁) which is placed at aposition a predetermined distance away in the −Y-direction fromreference axis LH in the periphery of projection unit PU, or morespecifically, on the −Y side of nozzle unit 32. Head units 62A and 62Care each also equipped with three Z heads which will be described lateron. Hereinafter, Y heads 65 ₁ to 65 ₅ and 64 ₁ to 64 ₅ will also bedescribed as Y heads 65 and 64, respectively, as necessary.

Head unit 62A constitutes a multiple-lens (five-lens, in this case) Ylinear encoder (hereinafter appropriately shortened to a “Y encoder” oran “encoder”) 70A (refer to FIG. 6) that measures the position of waferstage WST (wafer table WTB) in the Y-axis direction (the Y-position)using Y scale 39Y₁ previously described. Similarly, head unit 62Cconstitutes a multiple-lens (five-lens, in this case) Y linear encoder70C (refer to FIG. 6) that measures the Y-position of wafer stage WST(wafer table WTB) using Y scale 39Y₂ described above. In this case,distance WD in the X-axis direction of the five Y heads (64 or 65) (morespecifically, measurement beams) that head units 62A and 62C are eachequipped with, is set slightly narrower than the width (to be moreprecise, the length of grid line 38) of Y scales 39Y₁ and 39Y₂ in theX-axis direction.

As shown in FIG. 3, head unit 62B is placed on the +Y side of nozzleunit 32 (projection unit PU), and is equipped with a plurality of, inthis case, four X heads 66 ₅ to 66 ₈ that are placed on reference axisLV previously described along Y-axis direction at distance WD. Further,head unit 62D is placed on the −Y side of primary alignment system AL1,on the opposite side of head unit 62B via nozzle unit 32 (projectionunit PU), and is equipped with a plurality of, in this case, four Xheads 66 ₁ to 66 ₄ that are placed on reference axis LV at distance WD.Hereinafter, X heads 66 ₁ to 668 will also be described as X head 66, asnecessary.

Head unit 62B constitutes a multiple-lens (four-lens, in this case) Xlinear encoder (hereinafter, shortly referred to as an “X encoder” or an“encoder” as needed) 70B (refer to FIG. 6) that measures the position inthe X-axis direction (the X-position) of wafer stage WST (wafer tableWTB) using X scale 39X₁ described above. Further, head unit 62Dconstitutes a multiple-lens (four-lens, in this case) X linear encoder70D (refer to FIG. 6) that measures the X-position of wafer stage WST(wafer table WTB) using X scale 39X₂ previously described.

Here, the distance between adjacent X heads 66 (measurement beams) thatare equipped in each of head units 62B and 62D is set shorter than awidth in the Y-axis direction of X scales 39X₁ and 39X₂ (to be moreaccurate, the length of grid line 37). Further, the distance between Xhead 66 ₅ of head unit 62B farthest to the −Y side and X head 66 ₄ ofhead unit 62D farthest to the +Y side is set slightly narrower than thewidth of wafer stage WST in the Y-axis direction so that switching(linkage described below) becomes possible between the two X heads bythe movement of wafer stage WST in the Y-axis direction.

In the embodiment, furthermore, head units 62F and 62E are respectivelyarranged a predetermined distance away on the −Y side of head units 62Aand 62C. Although illustration of head units 62E and 62F is omitted inFIG. 3 and the like from the viewpoint of avoiding intricacy of thedrawings, in actual practice, head units 62E and 62F are fixed to theforegoing main frame that holds projection unit PU in a suspended statevia a support member. Incidentally, for example, in the case projectionunit PU is supported in a suspended state, head units 62E and 62F, andhead units 62A to 62D which are previously described can be supported ina suspended state integrally with projection unit PU, or can be arrangedat the measurement frame described above.

Head unit 62E is equipped with four Y heads 67 ₁ to 67 ₄ whose positionsin the X-axis direction are different. More particularly, head unit 62Eis equipped with three Y heads 67 ₁ to 67 ₃ placed on the −X side ofsecondary alignment system AL2 ₁ on reference axis LA previouslydescribed at substantially the same distance as distance WD previouslydescribed, and one Y head 67 ₄ which is placed at a position apredetermined distance (a distance slightly shorter than WD) away on the+X side from the innermost (the +X side) Y head 67 ₃ and is also on the+Y side of the secondary alignment system AL2 ₁ a predetermined distanceaway to the +Y side of reference axis LA.

Head unit 62F is symmetrical to head unit 62E with respect to referenceaxis LV, and is equipped with four Y heads 68 ₁ to 68 ₄ which are placedin symmetry to the four Y heads 67 ₄ to 67 ₁ described above withrespect to reference axis LV. Hereinafter, Y heads 67 ₁ to 67 ₄ and 68 ₁to 68 ₄ will also be described as Y heads 67 and 68, respectively, asnecessary. In the case of an alignment operation and the like which willbe described later on, at least one each of Y heads 67 and 68 faces Yscale 39Y₂ and 39Y₁, respectively, and by such Y heads 67 and 68 (morespecifically, Y encoders 70E and 70F which are configured by these Yheads 67 and 68), the Y position (and the θz rotation) of wafer stageWST is measured.

Further, in the embodiment, at the time of baseline measurement(Sec-BCHK (interval)) and the like of the secondary alignment systemswhich will be described later on, Y head 67 ₃ and 68 ₂ which areadjacent to secondary alignment systems AL2 ₁ and AL2 ₄ in the X-axisdirection face the pair of reference gratings 52 of FD bar 46,respectively, and by Y heads 67 ₃ and 68 ₂ that face the pair ofreference gratings 52, the Y position of FD bar 46 is measured at theposition of each reference grating 52. In the description below, theencoders configured by Y heads 67 ₃ and 68 ₂ which face a pair ofreference gratings 52, respectively, are referred to as Y linearencoders (also shortly referred to as a “Y encoder” or an “encoder” asneeded) 70E₂ and 70F₂ (refer to FIG. 6). Further, for identification, Yencoders 70E and 70F configured by Y heads 67 and 68 that face Y scales39Y₂ and 39Y₁ described above, respectively, will be referred to as Yencoders 70E₁ and 70F₁.

The six linear encoders 70A to 70F described above measure the positioncoordinates of wafer stage WST at a resolution of, for example, around0.1 nm, and the measurement values are supplied to main controller 20.Main controller 20 controls the position within the XY plane of wafertable WTB based on the measurement values of three of linear encoders70A to 70D or on the measurement values of three of encoders 70B, 70D,70E₁, and 70F₁, and also controls the rotation in the θz direction of FDbar 46 based on the measurement values of linear encoders 70E₂ and 70F₂.Incidentally, the configuration and the like of the linear encoder willbe described further later in the description.

In exposure apparatus 100 of the embodiment, as shown in FIG. 3, amultipoint focal position detecting system (hereinafter, shortlyreferred to as a “multipoint AF system”) by an oblique incident methodis arranged, which is composed of an irradiation system 90 a and aphotodetection system 90 b, having a configuration similar to the onedisclosed in, for example, Kokai (Japanese Unexamined Patent ApplicationPublication) No. 06-283403 (the corresponding U.S. Pat. No. 5,448,332)and the like. In the embodiment, as an example, irradiation system 90 ais placed on the +Y side of the −X end portion of head unit 62Epreviously described, and photodetection system 90 b is placed on the +Yside of the +X end portion of head unit 62F previously described in astate of opposing irradiation system 90 a.

A plurality of detection points of the multipoint AF system (90 a, 90 b)are placed at a predetermined distance along the X-axis direction on thesurface to be detected. In the embodiment, the plurality of detectionpoints are placed, for example, in the arrangement of a matrix havingone row and M columns (M is a total number of detection points) orhaving two rows and N columns (N is a half of a total number ofdetection points). In FIG. 3, the plurality of detection points to whicha detection beam is severally irradiated are not individually shown, butare shown as an elongate detection area (beam area) AF that extends inthe X-axis direction between irradiation system 90 a and photodetectionsystem 90 b. Because the length of detection area AF in the X-axisdirection is set to around the same as the diameter of wafer W, by onlyscanning wafer W in the Y-axis direction once, positional information(surface position information) in the Z-axis direction acrosssubstantially the entire surface of wafer W can be measured. Further,since detection area AF is placed between liquid immersion area 14(exposure area IA) and the detection areas of the alignment systems(AL1, AL2 ₁ to AL2 ₄) in the Y-axis direction, the detection operationsof the multipoint AF system and the alignment systems can be performedin parallel. The multipoint AF system may also be arranged on the mainframe that holds projection unit PU or the like, however, in theembodiment, the system will be arranged on the measurement framepreviously described.

Incidentally, the plurality of detection points are to be placed in onerow and M columns, or two rows and N columns, but the number(s) of rowsand/or columns is/are not limited to these numbers. However, in the casethe number of rows is two or more, the positions in the X-axis directionof detection points are preferably made to be different between thedifferent rows. Moreover, the plurality of detection points is to beplaced along the X-axis direction. However, the present invention is notlimited to this, and all of or some of the plurality of detection pointsmay also be placed at different positions in the Y-axis direction. Forexample, the plurality of detection points may also be placed along adirection that intersects both of the X-axis and the Y-axis. That is,the positions of the plurality of detection points only have to bedifferent at least in the X-axis direction. Further, a detection beam isto be irradiated to the plurality of detection points in the embodiment,but a detection beam may also be irradiated to, for example, the entirearea of detection area AF. Furthermore, the length of detection area AFin the X-axis direction does not have to be nearly the same as thediameter of wafer W.

In the vicinity of detection points located at both ends out of aplurality of detection points of the multipoint AF system (90 a, 90 b),that is, in the vicinity of both end portions of detection area AF,heads 72 a and 72 b, and 72 c and 72 d of surface position sensors for Zposition measurement (hereinafter, shortly referred to as “Z heads”) arearranged each in a pair, in symmetrical placement with respect toreference axis LV. Z heads 72 a to 72 d are fixed to the lower surfaceof a main frame (not shown). Incidentally, Z heads 72 a to 72 d may alsobe arranged on the measurement frame described above or the like.

As Z heads 72 a to 72 d, a sensor head that irradiates a light to wafertable WTB from above, receives the reflected light and measurespositional information of the wafer table WTB surface in the Z-axisdirection orthogonal to the XY plane at the irradiation point of thelight, as an example, a head of an optical displacement sensor (a sensorhead by an optical pickup method), which has a configuration like anoptical pickup used in a CD drive device, is used.

In the embodiment, as each Z head, a configuration is employed where thediffraction grating surfaces of Y scales 39Y₁ and 39Y₂ are observed fromabove (the +Z direction) as in the encoder. Accordingly, by measuringthe surface position information of the upper surface of wafer table WTBat different positions with the plurality of Z heads, the position ofwafer table WTB in the Z-axis direction and the θy rotation (rolling)can be measured.

Furthermore, head units 62A and 62C previously described are equippedwith Z heads 76 _(j) (j=3 to 5) and 74_(i) (i=1 to 3), which are threeheads each, respectively, at the same X position as Y heads 65 _(j) (j=3to 5) and 64_(i) (i=1 to 3) that head units 62A and 62C are respectivelyequipped with, with the Y position shifted. In this case, Z heads 76_(j) and 74 _(i), which are three heads each, belonging to head units62A and 62C, respectively, are placed parallel to reference axis LH apredetermined distance away in the +Y direction from reference axis LHand also symmetric to each other with respect to reference axis LV.Incidentally, as each of the Z heads 76 _(j) and 74 _(i), an opticaldisplacement sensor head similar to Z heads 72 a to 72 d described aboveis employed.

In this case, Z head 74 ₃ is on a straight line parallel to the Y-axis,the same as is with Z heads 72 a and 72 b previously described.Similarly, Z head 76 ₃ is on a straight line parallel to the Y-axis, thesame as is with Z heads 72 c and 72 d previously described.

Z heads 72 a to 72 d, Z heads 74 ₁ to 74 ₃, and Z heads 76 ₃ to 76 ₅connect to main controller 20 via a signal processing/selection device170 as shown in FIG. 6, and main controller 20 selects an arbitrary Zhead from Z heads 72 a to 72 d, Z heads 74 ₁ to 74 ₃, and Z heads 76 ₃to 76 ₅ via signal processing/selection device 170 and makes the headmove into an operating state, and then receives the surface positioninformation detected by the Z head which is in an operating state viasignal processing/selection device 170. In the embodiment, a surfaceposition measurement system 180 that measures positional information ofwafer table WTB in the Z-axis direction and the direction of inclinationwith respect to the XY plane is configured, including Z heads 72 a to 72d, Z heads 74 ₁ to 74 ₃, and Z heads 76 ₃ to 76 ₅, and signalprocessing/selection device 170.

Incidentally, in FIG. 3, measurement stage MST is omitted and a liquidimmersion area that is formed by water Lq held in the space betweenmeasurement stage MST and tip lens 191 is shown by a reference code 14.Further, as shown in FIG. 3, in the embodiment, unloading position UPand loading position LP are set symmetrically with respect to referenceaxis LV. However, as well as this, unloading position UP and loadingposition LP can be at the same position.

FIG. 6 shows the main configuration of the control system of exposureapparatus 100. The control system is mainly configured of maincontroller 20 composed of a microcomputer (or workstation) that performsoverall control of the entire apparatus. In memory 34 which is anexternal memory connected to main controller 20, correction informationis stored of measurement instrument systems such as interferometersystem 118, encoder system 150 (encoders 70A to 70F), Z heads 72 a to 72d, 74 ₁ to 74 ₃, 76 ₃ to 76 ₅ and the like. Incidentally, in FIG. 6,various sensors such as uneven illuminance measuring sensor 94, aerialimage measuring instrument 96 and wavefront aberration measuringinstrument 98 that are arranged at measurement stage MST arecollectively shown as a sensor group 99.

Next, the configuration and the like of encoders 70A to 70F will bedescribed, focusing on Y encoder 70C that is shown enlarged in FIG. 7Aas a representative. FIG. 7A shows one Y head 64 of head unit 62C thatirradiates a detection light (measurement beam) to Y scale 39Y₂.

Y head 64 is mainly composed of three sections, which are an irradiationsystem 64 a, an optical system 64 b and a photodetection system 64 c.

Irradiation system 64 a includes a light source that emits a laser beamLB in a direction inclined at an angle of 45 degrees with respect to theY-axis and Z-axis, for example, a semiconductor laser LD, and a lens L1that is placed on the optical path of laser beam LB emitted fromsemiconductor laser LD.

Optical system 64 b is equipped with a polarization beam splitter PBSwhose separation plane is parallel to an XZ plane, a pair of reflectionmirrors R1 a and R1 b, lenses L2 a and L2 b, quarter wavelength plates(hereinafter, referred to as a λ/4 plate) WP1 a and WP1 b, reflectionmirrors R2 a and R2 b, and the like. In this case, reflection mirror R1b is placed at position symmetric to reflection mirror R1 a, with aseparation plane of polarization beam splitter PBS serving as areference. Similarly, converging lens L2 a and L2 b, λ/4 plates WP1 aand WP1 b, and reflection mirrors R2 a and R2 b are also placed atpositions symmetric to each other, with the separation plane ofpolarization beam splitter PBS serving as a reference.

Photodetection system 64 c includes a polarizer (analyzer), aphotodetector, and the like. Photodetection system 64 c is placed on areturn optical path of the reflection diffraction light of laser beam LBvia the separation plane of polarization beam splitter PBS.

In Y encoder 70C, laser beam LB emitted from semiconductor laser LD isincident on polarization beam splitter PBS via lens L1, and is split bypolarization into two beams LB₁ and LB₂. In this case, a P-polarizationcomponent of laser beam LB passes through polarization beam splitter PBSand forms beam LB₁, and an S-polarization component is reflected off theseparation plane of polarization beam splitter PBS and forms beam LB₂.Beam LB₁ and LB₂ are reflected off reflection mirrors R1 a and R1 b,respectively, and are incident on reflection grating RG.

Diffraction light is generated by beams LB₁ and LB₂ being irradiated onreflection grating RG. Of diffraction lights equal to or less than the−1st order generated by the irradiation of beam LB₁, for example, adiffraction light of the −1st order passes through converging lens L2 aand λ/4 plate WP1 a, and reaches reflection mirror R2 a. However, thesign of the order of the diffraction light is defined so that thediffraction light diffracting in the +Y direction (−Y direction) ispositive (negative), with a zero-order diffraction light reflected bythe same angle as the incoming light serving as a reference, as it willbe described later on. Then, the diffraction light is reflected byreflecting mirror R2 a, and by tracing the same optical path as theoutward path in the opposite direction, the light reaches reflectiongrating RG. In this case, by passing through λ/4 plate WP1 a twice inthe outward path and the return path, the polarization direction of thediffraction light rotates by 90 degrees, and the diffraction light isconverted into S-polarization. Meanwhile, of the diffraction light equalto or more than the +1st order generated by the irradiation of beam LB₂,for example, a diffraction light of the +1st order passes throughconverging lens L2 b and λ/4 plate WP1 b, and reaches reflection mirrorR2 b. Then, the diffraction light is reflected by reflecting mirror R2b, and by tracing the same optical path as the outward path in theopposite direction, the light reaches reflection grating RG. In thiscase, by passing through λ/4 plate WP1 b twice in the outward path andthe return path, the polarization direction of the diffraction lightrotates by 90 degrees, and the diffraction light is converted intoP-polarization.

By the irradiation of the return diffraction light from reflectionmirrors R2 a and R2 b on reflection grating RG, a diffraction light isgenerated again. Of the diffraction lights deriving from the returnlight from reflection mirror R2 a, diffraction light of the same orderas the return light is reflected by reflection mirror R1 a and thenreaches polarization beam splitter PBS. Meanwhile, of the diffractionlights deriving from the return light from reflection mirror R2 b,diffraction light of the same order as the return light is reflected byreflection mirror R1 b and then reaches polarization beam splitter PBS.

Return beams LB₁ and LB₂ that reach polarization beam splitter PBS areconverted into S-polarization and P-polarization, respectively.Therefore, return beam LB₁ is reflected by the separation plane ofpolarization beam splitter PBS, and return beam LB₂ passes throughpolarization beam splitter PBS. Accordingly, return beams LB₁ and LB₂are synthesized coaxially, and are incident on photodetection system 64c.

In the inside of photodetection system 64 c, an analyzer arranges thepolarization direction of return beams LB₁ and LB₂ and makes the beamsoverlap so as to form an interference light. This interference light isdetected by the photodetector. In this case, when Y scale 39Y₂ (morespecifically wafer stage WST) moves in the measurement direction (inthis case, the Y-axis direction), phase difference between the two beamsLB₁ and LB₂ changes as it will be described later on, which causes theintensity of the interference light to change. From this intensitychange of the interference light, the positional relation between Y head64 and Y scale 39Y₂, or more specifically, the Y-coordinate of waferstage WST is computed and is output as a measurement value of Y encoder70A.

Incidentally, other Y heads 64 of head unit 62C, and each of the Y heads65 belonging to head unit 62A are configured similarly as in thedescription above, and the heads face Y scale 39Y₂ or 39Y₁ and make up Yencoder 70C or 70A.

Further each of the X heads 66 belonging to head units 62B and 62D,respectively, are configured similarly to Y head 64 described above, andthe heads face X scale 39X₁ or 39X₂ and make up X encoder 70B or 70D.

Further, each of the Y heads 67 and 68 belonging to head units 62E and62F, respectively, are configured similarly to Y head 64 describedabove, and the heads face Y scale 39Y₂ or 39Y₁ and make up Y encoder70E₁ or 70F₁. Further, Y heads 67 ₃ and 68 ₂ face the pair of referencegratings 52 on measurement stage MST, respectively, and make up Yencoders 70E₂ and 70F₂.

As each encoder, an encoder having a resolution of, for example, around0.1 nm is used. Incidentally, in the encoders of the embodiment, asshown in FIG. 7B, laser beam LB having a sectional shape that iselongated in the periodic direction of diffraction grating RG may alsobe used, as a detection light. In FIG. 7B, beam LB is overdrawn largelycompared to grating RG.

Incidentally, as another form of the encoder head, there is a type inwhich only optical system 64 b is included in the encoder head andirradiation system 64 a and photodetection system 64 c are physicallyseparate from optical system 64 b. In the case of such a type, the laserbeam is guided between these three sections via an optical fiber.

Next, a parallel processing operation that uses wafer stage WST andmeasurement stage MST in exposure apparatus 100 of the embodiment willbe described based on FIGS. 8 to 11. Incidentally, during the operationbelow, main controller 20 performs the open/close control of each valveof liquid supply device 5 of local liquid immersion device 8 and liquidrecovery device 6 in the manner previously described, and water isconstantly filled on the outgoing surface side of tip lens 191 ofprojection optical system PL. However, in the description below, for thesake of simplicity, the explanation related to the control of liquidsupply device 5 and liquid recovery device 6 will be omitted. Further,many drawings are used in the operation description hereinafter;however, reference codes may or may not be given to the same member foreach drawing. More specifically, the reference codes written aredifferent for each drawing; however, such members have the sameconfiguration, regardless of the indication of the reference codes. Thesame can be said for each drawing used in the description so far.

FIG. 8 shows a state in which an exposure by the step-and-scan method ofwafer W mounted on wafer stage WST is performed. This exposure isperformed by alternately repeating a movement between shots in whichwafer stage WST is moved to a scanning starting position (accelerationstaring position) to expose each shot area on wafer W and scanningexposure in which the pattern formed on reticle R is transferred ontoeach shot area by the scanning exposure method, based on results ofwafer alignment (e.g., Enhanced Global Alignment (EGA)) and the likewhich has been performed prior to the beginning of exposure. Further,exposure is performed in the following order, from the shot area locatedon the −Y side on wafer W to the shot area located on the +Y side.Incidentally, exposure is performed in a state where liquid immersionarea 14 is formed in between projection unit PU and wafer W.

During the exposure described above, the position (including rotation inthe θz direction) of wafer stage WST (wafer table WTB) in the XY planeis controlled by main controller 20, based on measurement results of atotal of three encoders which are the two Y encoders 70A and 70C, andone of the two X encoders 70B and 70D. In this case, the two X encoders70B and 70D are made up of two X heads 66 that face X scale 39X₁ and39X₂, respectively, and the two Y encoders 70A and 70C are made up of Yheads 65 and 64 that face Y scales 39Y₁ and 39Y₂, respectively. Further,the Z position and rotation (rolling) in the θy direction of wafer stageWST are controlled, based on measurement results of a pair of Z heads 74_(i) and 76 _(j) that respectively faces the end section on one side andthe other side of the surface of wafer table WTB in the X-axisdirection. The θx rotation (pitching) of wafer stage WST is controlled,based on measurement results of Y interferometer 16. Incidentally, thecontrol of the position of wafer table WTB in the Z-axis direction, therotation in the θy direction, and the rotation in the θx direction (morespecifically, the focus leveling control of wafer W) is performed, basedon results of a focus mapping performed beforehand.

At the position of wafer stage WST shown in FIG. 8, while X head 66 ₅(shown circled in FIG. 8) faces X scale 39X₁, there are no X heads 66that face X scale 39X₂. Therefore, main controller 20 uses one X encoder70B and two Y encoders 70A and 70C so as to perform position (X, Y, Oz)control of wafer stage WST. In this case, when wafer stage WST movesfrom the position shown in FIG. 8 to the −Y direction, X head 66 ₅ movesoff of (no longer faces) X scale 39X₁, and X head 66 ₄ (shown circled ina broken line in FIG. 8) faces X scale 39X₂ instead. Therefore, maincontroller 20 switches the stage control to a control that uses one Xencoder 70D and two Y encoders 70A and 70C.

In this manner, main controller 20 performs stage control byconsistently switching the encoder to use depending on the positioncoordinate of wafer stage WST.

Incidentally, independent from the position measurement of wafer stageWST described above using the encoders, position (X, Y, Z, θx, θy, θz)measurement of wafer stage WST using interferometer system 118 isconstantly performed. In this case, the X position and θz rotation(yawing) of wafer stage WST are measured using X interferometers 126,127, or 128, the Y position, the θx rotation, and the θz rotation aremeasured using Y interferometer 16, and the Y position, the Z position,the θy rotation, and the θz rotation are measured using Zinterferometers 43A and 43B (not shown in FIG. 8, refer to FIG. 1 or 2)that constitute interferometer system 118. Of X interferometers 126,127, and 128, one interferometer is used according to the Y position ofwafer stage WST. As indicated in FIG. 8, X interferometer 126 is usedduring exposure. The measurement results of interferometer system 118regarding the directions of three degrees of freedom in the X, Y, and θzdirections are used secondarily for position control of wafer stage WST.

When exposure of wafer W has been completed, main controller 20 driveswafer stage WST toward unload position UP. On this drive, wafer stageWST and measurement stage MST which were apart during exposure come intocontact or move close to each other with a clearance of around 300 μm inbetween, and shift to a scrum state. In this case, the −Y side surfaceof CD bar 46 on measurement table MTB and the +Y side surface of wafertable WTB come into contact or move close together. And by moving bothstages WST and MST in the −Y direction while maintaining the scrumcondition, liquid immersion area 14 formed under projection unit PUmoves to an area on measurement stage MST. For example, FIGS. 9 and 10show the state after the movement.

When wafer stage WST moves further to the −Y direction and moves offfrom the effective stroke area (the area in which wafer stage WST movesat the time of exposure and wafer alignment), all the X heads and Yheads, and all the Z heads that constitute encoder 70A to 70D move offfrom the corresponding scales on wafer table WTB. Therefore, stagecontrol based on the measurement results of encoders 70A to 70D and theZ heads is no longer possible. Just before this, main controller 20switches the stage control to a control based on the measurement resultsof interferometer system 118. In this case, of the three Xinterferometers 126, 127, and 128, X interferometer 128 is used.

Then, as shown in FIG. 9, wafer stage WST releases the scrum state withmeasurement stage MST, and then moves to unload position UP. After themovement, main controller 20 unloads wafer W on wafer table WTB. Andthen, as shown in FIG. 10, wafer stage WST is driven in the +X directionto loading position LP, and the next wafer W is loaded on wafer tableWTB.

In parallel with these operations, main controller 20 performs Sec-BCHK(a secondary base line check) in which position adjustment of FD bar 46supported by measurement stage MST in the XY plane and baselinemeasurement of the four secondary alignment system AL2 ₁ to AL2 ₄ areperformed. Sec-BCHK is performed on an interval basis for every waferexchange. In this case, in order to measure the position (the θzrotation) in the XY plane, Y encoders 70E₂ and 70F₂ previously describedare used.

Next, as shown in FIG. 11, main controller 20 drives wafer stage WST andpositions fiducial mark FM on measurement plate 30 within a detectionfield of primary alignment system AL1, and performs the former processof Pri-BCHK (a primary baseline check) in which the reference positionis decided for baseline measurement of alignment system AL1, and AL2 ₁to AL2 ₄.

On this process, as shown in FIG. 11, two Y heads 68 ₂ and 67 ₃ and oneX head 66 ₁ (shown circled in the drawing) come to face Y scales 39Y₁and 39Y₂, and X scale 39X₂, respectively. Then, main controller 20switches the stage control from a control using interferometer system118, to a control using encoder system 150 (encoders 70A, 70C, and 70D).Interferometer system 118 is used secondarily again. Incidentally, ofthe three X interferometers 126, 127, and 128, X interferometer 127 isused.

Then, main controller 20 performs wafer alignment (EGA), using primaryalignment system AL1 and secondary alignment systems AL2 ₁ to AL2 ₄(refer to the star mark in FIG. 12).

Incidentally, in the embodiment, as shown in FIG. 12, wafer stage WSTand measurement stage MST are to be shifted to the scrum state by thetime wafer alignment begins. Main controller 20 drives both stages WSTand MST in the +Y direction, while maintaining the scrum state. Then,the water of liquid immersion area 14 is moved from above measurementtable MTB to an area on wafer table WTB.

In parallel with a wafer alignment (EGA), main controller 20 performsfocus calibration and focus mapping using the Z heads (70 a to 70 d) andthe multipoint AF system (90 a, 90 b), and furthermore performs thelatter process of Pri-BCHK in which intensity distribution of aprojection image of wafer table WTB with respect to the XY position ismeasured using aerial image measuring device 45.

When the operation described above has been completed, main controller20 releases the scrum state of both stages WST and MST. And, as shown inFIG. 8, exposure by the step-and-scan method is performed, and a reticlepattern is transferred onto a new wafer W. Hereinafter, a similaroperation is executed repeatedly.

Next, a measurement principle of an encoder will be explained in detail,with Y encoder 70C shown in FIG. 7A serving as an example. First of all,a relation between the intensity of interference light that issynthesized from two return beams LB₁ and LB₂ and displacement (relativedisplacement with Y head 64) of Y scale 39Y₂ is derived.

When the two beams LB₁ and LB₂ are scattered by reflection grating RGthat moves, the beams are subject to a frequency shift by a Dopplereffect, or in other words, undergo a Doppler shift. FIG. 13A shows ascatter of light by the moving reflection surface DS. However, vectorsk₀ and k₁ in the drawing are to be parallel with a YZ plane, andreflection surface DS is to be parallel to the Y-axis and perpendicularto the Z-axis.

Supposing that reflection surface DS moves at a velocity vector v=vy+vz,or more specifically, moves in the +Y direction at a speed Vy (=|vy|)and also in the +Z direction at a speed Vz (=|vz|). To this reflectionsurface, the light of wave number vector k₀ is incident at an angle θ₀,and the light of wave number vector k₁ is scattered at an angle θ₁.However, |k₀|=|k₁|=K. Doppler shift (frequency difference of scatteredlight k₁ and incident light k₀) f_(D) that incident light k₀ undergoesis given in the next formula (7).

$\begin{matrix}\begin{matrix}{{2\pi \; f_{D}} = {\left( {k_{1} - k_{0}} \right) \cdot v}} \\{= {2{KVy}\; {\cos \left\lbrack {\left( {\theta_{1} - \theta_{0}} \right)/2} \right\rbrack}\cos \; \theta}} \\{= {2{KVz}\; {\cos \left\lbrack {\left( {\theta_{1} - \theta_{0}} \right)/2} \right\rbrack}\sin \; \theta}}\end{matrix} & (7)\end{matrix}$

In this case, since θ=π/2−(θ₁+θ₀)/2, formula (7) above is transformed soas to obtain the following formula (8).

2πf _(D) =KVy(sin θ₁+sin θ₀)+KVz(cos θ₁+cos θ₀)  (8)

Reflection surface DS is displaced during time Δt by displacement vectorvΔt, or more specifically, displaced in the +Y direction by a distanceΔY=VyΔt and in the +Z direction by a distance ΔZ=VzΔt. And with thisdisplacement, the phase of scattered light k₁ shifts by φ=2πf_(D)Δt.Phase shift φ can be obtained from the following formula (9) whenformula (8) is substituted.

φ=KΔY(sin θ₁+sin θ₀)+KΔZ(cos θ₁+cos θ₀)  (9)

In this case, a relation (a diffraction condition) expressed as informula (10) below is valid between incident angle θ₀ and scatteringangle θ₁.

sin θ₁+sin θ₀ =nλ/p  (10)

However, λ is the wavelength of the light, p is the pitch of thediffraction grating, and n is the order of diffraction. Incidentally,order of diffraction n becomes positive to a diffraction light scatteredin the +Y direction, and becomes negative to a diffraction lightscattered in the −Y direction, with a zero order diffraction light ofscattering angle −θ₀ serving as a reference. Phase shift φ can berewritten as in formula (11) below when formula (10) is substituted informula (9).

φ=2πnΔY/p+KΔZ(cos θ₁+cos θ₀)  (11)

As is obvious from formula (11) above, if reflection surface DS stops,or more specifically, ΔY=ΔZ=0, phase shift φ also becomes zero.

Using formula (11), phase shift of the two beams LB₁ and LB₂ isobtained. First of all, phase shift of beam LB₁ will be considered. InFIG. 13B, supposing that beam LB₁, which was reflected off reflectionmirror R1 a, is incident on reflection grating RG at an angle θ_(a0),and a n_(a) order diffraction light is to be scattered at an angleθ_(a1). When the diffraction light is generated, the phase shift thatthe diffraction light undergoes becomes the same form as the right-handside of formula (11). And the return beam, which is reflected offreflection mirror R2 a and follows the return path, is incident onreflection grating RG at angle θ_(a1). Then, a diffraction light isgenerated again. In this case, the diffraction light that is scatteredat angle θ_(a0) and moves toward reflection mirror R1 a following theoriginal optical path is an n_(a) order diffraction light, which is adiffraction light of the same order as the diffraction light generatedon the outward path. Accordingly, the phase shift which beam LB₁undergoes on the return path is equal to the phase shift which beam LB₁undergoes on the outward path. Accordingly, the total phase shift whichbeam LB₁ undergoes is obtained as in the following formula (12).

φ₁=4πn _(a) ΔY/p+2KΔZ(cos θ_(a1)+cos θ_(a0))  (12)

However, a diffraction condition was given as in the next formula (13).

sin θ_(a1)+sin θ_(a0) =n _(a) λ/p  (13)

Meanwhile, beam LB₂ is incident on reflection grating RG at an angleθ_(b0), and an n_(b) order diffraction light is scattered at an angleθ_(b1). Supposing that this diffraction light is reflected offreflection mirror R2 b and returns to reflection mirror R1 b followingthe same optical path. The total phase shift which beam LB₂ undergoescan be obtained as in the next formula (14), similar to formula (12).

φ₂=4πn _(b) ΔY/p+2KΔZ(cos θ_(b1)+cos θ_(b0))  (14)

However, a diffraction condition was given as in the next formula (15).

sin θ_(b1)+sin θ_(b0) =n _(b) λ/p  (15)

Intensity I of the interference light synthesized by the two returnbeams LB₁ and LB₂ is dependent on a phase difference φ between the tworeturn beams LB₁ and LB₂ in the light receiving position of thephotodetector, by I∝1+cos φ. However, the intensity of the two beams LB₁and LB₂ was to be equal to each other. In this case, phase difference φcan be obtained as a sum of a difference (more specifically φ2−φ1) ofphase shifts due to Y and Z displacements of each reflection grating RGof the two beams LB₁ and LB₂ and a phase difference (KΔL) due to opticalpath difference ΔL of the two beams LB₁ and LB₂, as in formula (16)below.

φ=KΔL+4π(n _(b) −n _(a))ΔY/p+2KΔZf(θ_(a0),θ_(a1),θ_(b0),θ_(b1))+φ₀  (16)

Here, formulas (12) and (14) were used. Incidentally, a geometricfactor, which is to be decided from the placement of reflection mirrorsR1 a, R1 b, R2 a, and R2 b and the diffraction conditions, was expressedas in formula (17) below.

f(θ_(a0),θ_(a1),θ_(b0),θ_(b1))=cos θ_(b1)+cos θ_(b0)−cos θ_(a1)−cosθ_(a0)  (17)

Further, a constant phase term, which is to be decided by other factors(e.g., a definition of the reference position of displacements ΔL, ΔY,and ΔZ), was expressed as φ0.

In this case, the encoder is to be configured so as to satisfy opticalpath difference ΔL=0 and a symmetry shown in the following formula (18).

θ_(a0)=θ_(b0),θ_(a1)=θ_(b1)  (18)

In such a case, inside the parenthesis of the third term on theright-hand side of formula (16) becomes zero, and also at the same timen_(b)=−n_(a) (=n), therefore, the following formula (19) can beobtained.

φ_(sym)(ΔY)=2πΔY/(p/4n)+φ₀  (19)

From formula (19) above, it can be seen that phase difference φ_(sym) isnot dependent on wavelength λ of the light. And, it can be seen thatintensity I of the interference light repeats strong and weakintensities each time displacement ΔY is increased or decreased by ameasurement unit (also referred to as a measurement pitch) of p/4n.Therefore, the number of times is measured of the strong and weakintensities of the interference light that accompanies displacement ΔYfrom a predetermined reference position. And, from counter value (countvalue) c_(ΔY), measurement value C_(ΔY) of displacement ΔY is obtainedas in the following formula (20).

C _(ΔY)=(p/4n)×c _(ΔY)  (20)

Furthermore, by splitting a sinusoidal intensity change of theinterference light using an interpolation instrument (an interpolator),its phase φ′ (=φ_(sym)% 2π) can be measured. In this case, measurementvalue C_(ΔY) of displacement ΔY is computed according to the followingformula (21).

C _(ΔY)=(p/4n)×{c _(ΔY)+(φ′−φ₀)/2π}  (21)

In this case, constant phase term φ₀ is to be a phase offset (however,0≦φ₀<2π), and phase φ_(sym) (ΔY=0) at the reference position ofdisplacement ΔY is to be kept.

As it can be seen from the description so far above, by using aninterpolation instrument together, displacement ΔY can be measured at ameasurement resolution whose measurement unit is (p/4n) or under. Themeasurement resolution in this case is decided from a discretizationerror (also referred to as a quantization error) determined from a splitunit of phase φ′, an interpolation error due to a shift of an intensitychange I(ΔY)=I(φ_(sym)(ΔY)) of the interference light from an idealsinusoidal waveform according to displacement ΔY, or the like.Incidentally, because the discretization unit of displacement ΔY is, forexample, one in several thousand of measurement unit (p/4n), which issufficiently small about 0.1 nm, measurement value C_(ΔY) of the encoderwill be regarded as a continuous quantity unless it is noted otherwise.

Meanwhile, when wafer stage WST moves in a direction different from theY-axis direction and a relative displacement occurs between Y head 64and Y scale 39Y₂ in a direction besides the measurement direction, ameasurement error occurs in Y encoder 70C. In the description below, ageneration mechanism of a measurement error will be considered, based onthe measurement principle of the encoder described above.

As a simple example, the change of phase difference φ indicated byformula (16) above in the two cases shown in FIGS. 14A and 14B will beconsidered. First of all, in the case of FIG. 14A, the optical axis ofhead 64 coincides with the Z-axis direction (head 64 is not inclined).Assuming that wafer stage WST is displaced in the Z-axis direction(ΔZ≠0, ΔY=0). In this case, because there are no changes in optical pathdifference ΔL, there are no changes in the first term on the right-handside of formula (16). The second term becomes zero, according to asupposition ΔY=0. And, the third term becomes zero because it satisfiesthe symmetry of formula (18). Accordingly, no change occurs in phasedifference φ, and further no intensity change of the interference lightoccurs. As a consequence, the measurement values of the encoder also donot change.

Meanwhile, in the case of FIG. 14B, the optical axis of head 64 isinclined (head 64 is inclined) with respect to the Z-axis. Assuming thatwafer stage WST was displaced in the Z-axis direction from this state(ΔZ≠0, ΔY=0). In this case as well, because there are no changes inoptical path difference ΔL, there are no changes in the first term onthe right-hand side of formula (16). And, the second term becomes zero,according to supposition ΔY=0. However, because the head is inclined thesymmetry of formula (18) will be lost, and the third term will notbecome zero and will change in proportion to Z displacement ΔZ.Accordingly, a change occurs in phase difference φ, and as aconsequence, the measurement value changes.

Further, although it is omitted in the drawings, in the case wafer stageWST is displaced in a direction perpendicular to the measurementdirection (the Y-axis direction) and the optical axis direction (theZ-axis direction), (ΔX≠0, ΔY=0, ΔZ=0), the measurement values do notchange as long as the direction in which the grid line of diffractiongrating RG faces is orthogonal to the measurement direction, however, inthe case the direction is not orthogonal, sensitivity occurs with a gainproportional to the angle.

Next, a case will be considered in which wafer stage WST rotates (theinclination changes), using FIGS. 15A to 15D. First of all, in FIG. 15A,the optical axis of head 64 coincides with the Z-axis direction (head 64is not inclined). Even if wafer stage WST is displaced in the +Zdirection and moves to a condition shown in FIG. 15B from this state,the measurement value of the encoder does not change since the case isthe same as in FIG. 14A previously described.

Next, assume that wafer stage WST rotates around the X-axis from thestate shown in FIG. 15B and moves into a state shown in FIG. 15C. Inthis case, even though the head and the scale do not perform relativemotion, or more specifically, even though ΔY=ΔZ=0, a change occurs inoptical path difference ΔL due to the rotation of wafer stage WST, andtherefore the measurement values of the encoder change.

Next, suppose that wafer stage WST moves downward from a state shown inFIG. 15C and moves into a state shown in FIG. 15D. In this case, achange in optical path difference ΔL does not occur because wafer stageWST does not rotate. However, because the symmetry of formula (18) hasbeen lost, phase difference φ changes by Z displacement ΔZ through thethird term on the right-hand side of formula (16). Accordingly, themeasurement value of the encoder changes.

As other generation factors of measurement errors, temperaturefluctuation (air fluctuation) of the atmosphere on the beam optical pathcan be considered. Phase difference φ between the two return beams LB₁and LB₂ depend on optical path difference ΔL of the two beams, accordingto the first term on the right-hand side of formula (16). In this case,assume that wavelength λ of the light changes to λ+Δλ by airfluctuation. By minute change Δλ of this wavelength, the phasedifference changes by minute amount Δφ=2πΔLΔλ/λ². In this case, when thewavelength of light λ=1 μm and minute change Δλ=1 nm, then phase changeΔφ=2π with respect to optical path difference ΔL=1 mm. This phase changeis equivalent to 1 when it is converted into a count value of theencoder. Further, when it is converted into displacement, it isequivalent to p/2 (n_(b)−n_(a)). Accordingly, if n_(b)=−n_(a)=1, in thecase of p=1 μm, a measurement error of 0.25 μm will occur.

In the actual encoder, because the optical path length of the two beamswhich are made to interfere is extremely short, wavelength change Δλ dueto the air fluctuation is extremely small. Furthermore, optical pathdifference ΔL is designed to be approximately 0, in an ideal state wherethe optical axis is orthogonal to the reflection surface. Therefore, themeasurement errors due to the air fluctuation can be substantiallyignored. The fluctuation is remarkably small when compared with theinterferometer, and is superior in short-term stability.

As key factors of measurement errors of the encoder, errors which arecaused by an uneven scale surface, or mechanical deformation of thediffraction grating and the like can be given. With the passage of usetime and also thermal expansion or the like, the surface is deformed inthe scale of the encoder, or the pitch of the diffraction grating ischanged partially or entirely. Therefore, the encoder has a tendency inwhich measurement errors grow larger with the passage of use time, andlacks in long-term stability.

Therefore, after having performed pre-processing to correct these mainerrors beforehand, the encoder is used in position measurement of waferstage WST which is executed during the actual processing of a lot.

Main controller 20 by all means monitors the measurement values of atotal of at least three encoders, which are encoders 70A and 70C, and atleast one of encoders 70B and 70D in the effective stroke range of waferstage WST, and computes the position coordinate of wafer stage WST.Then, by controlling each motor that configures stage drive system 124according to the position coordinate which has been calculated, waferstage WST can be driven with high precision.

Now, a method to compute the position coordinate of wafer stage WST fromthe measurement values of the three encoders which are monitored will bedescribed, using FIGS. 16A and 16B. In this case, for the sake ofsimplicity, the degrees of freedom of the movement of wafer stage WSTwill be three (X, Y, θz).

FIG. 16A shows a reference state where wafer stage WST is at the originof coordinates (X, Y, θz)=(0, 0, 0). From this reference state, waferstage WST is driven within a range where encoders (Y heads) Enc1 andEnc2 and encoder (X head) Enc3 do not move away from the scanning areasof their opposing scales 39Y₁ and 39Y₂ and 39X₁. The state where waferstage WST is moved to position (X, Y, θz) in the manner described aboveis shown in FIG. 16B. However, the setting position (X, Y) of encodersEnc1, Enc2, and Enc3 on the XY coordinate system are to be (p₁, q₁),(p₂, q₂), and (p₃, q₃), respectively.

The X head and the Y head respectively measure the relative distancefrom central axes LL and LW of wafer stage WST. Accordingly, measurementvalues C_(X) and C_(Y) of the X head and the Y head can be expressed,respectively, as in the following formulas (22a) and (22b).

C _(X) =r′·ex′  (22a)

C _(Y) =r′·ey′  (22b)

In this case, ex′ and ey′ are X′ and Y′ unit vectors in a relativecoordinate system (X′, Y′, θz′) set on wafer stage WST, and have arelation as in the following formula (23) with X and Y unit vectors exand ey in the reference coordinate system (X, Y, θz).

$\begin{matrix}{\begin{pmatrix}{ex}^{\prime} \\{ey}^{\prime}\end{pmatrix} = {\begin{pmatrix}{\cos \; \theta \; z} & {\sin \; \theta \; z} \\{{- \sin}\; \theta \; z} & {\cos \; \theta \; z}\end{pmatrix}\begin{pmatrix}{ex} \\{ey}\end{pmatrix}}} & (23)\end{matrix}$

Further, r′ is a position vector of the encoder in the relativecoordinate system, and r′ is given r′=r−(O′−O), using position vectorr=(p, q) in the reference coordinate system. Accordingly, formulas (22a)and (22b) are rewritten as in formulas (24a) and (24b) below.

C _(X)=(p−X)cos θz+(q−Y)sin θz  (24a)

C _(Y)=−(p−X)sin θz+(q−Y)cos θz  (24b)

Accordingly, when wafer stage WST is located at the coordinate (X, Y,θz) as shown in FIG. 16B, the measurement values of three encoders canbe expressed theoretically as in the next formulas (25a) to (25c).

C ₁=−(p ₁ −X)sin θz+(q ₁ −Y)cos θz  (25a)

C ₂=−(p ₂ −X)sin θz+(q ₂ −Y)cos θz  (25b)

C ₃=(p ₃ −X)cos θz+(q ₃ −Y)sin θz  (25c)

Incidentally, in the reference state shown in FIG. 16A, according tosimultaneous equations (25a) to (25c), then C₁=q₁, C₂=q₂, and C₃=p₃.Accordingly, in the reference state, if the measurement values of thethree encoders Enc1, Enc2, and Enc3 are initialized to q₁, q₂, and p₃respectively, then the three encoders will show theoretical values givenby formulas (25a) to (25c) with respect to displacement (X, Y, θz) ofwafer stage WST from then onward.

In simultaneous equations (25a) to (25c), three formulas are given tothe three variables (X, Y, θz). Accordingly, on the contrary, ifdependent variables C₁, C₂, and C₃ are given in the simultaneousequations (25a) to (25c), variables X, Y, and θz can be obtained. Inthis case, when approximation sin θz≈θz is applied, or even if anapproximation of a higher order is applied, the equations can be solvedeasily. Accordingly, the position of wafer stage WST (X, Y, θz) can becomputed from measurement values C₁, C₂, and C₃ of the encoder.

In exposure apparatus 100 of the embodiment, as exemplified in FIGS. 17Aand 17B, in the effective stroke range (a range where the stage movesfor alignment and exposure operation) of wafer stage WST, Y scales and Yheads are placed so that Y scales 39Y₁ and 39Y₂ each have at least one Yhead (65, 64, 68 or 67) facing the scales without fail. And, X scalesand X heads are placed so that at least one of X scales 39X₁ and 39X₂has at least one X head 66 facing the scale. Accordingly, at least threeheads are placed to simultaneously face the corresponding X scales and Yscales. Incidentally, in FIGS. 17A and 17B, the heads which face thecorresponding X scales and Y scales are shown surrounded in a circle.

In this case, when main controller 20 drives wafer stage WST in the +Xdirection as is shown by an outlined arrow in FIG. 17A, main controller20 switches Y head 64, for example, as shown by an arrow e₁ in thedrawing, from Y head 64 ₃ surrounded in a circle with a solid line tohead 64 ₄ surrounded in a circle with a dotted line. As is described, Yhead 64 is sequentially switched to the next head, with the movement ofwafer stage WST in the X-axis direction. Incidentally, because theencoder detects relative displacement, in order to compute absolutedisplacement (more specifically, the position) a position which will bea reference has to be set. Therefore, on the switching of the heads, theposition of an operating head is computed and is initialized as areference position. The initial setting will be explained later indetail.

Further, in the case main controller 20 drives wafer stage WST in the +Ydirection as is shown by an outlined arrow in FIG. 17B, main controller20 switches X head 66, for example, as shown by an arrow e₂ in thedrawing, from head 66 ₅ surrounded in a circle with a solid line to head66 ₆ surrounded in a circle with a dotted line. As is described, X head66 is sequentially switched to the next head, with the movement of waferstage WST in the Y-axis direction. On this head switching, the positionof an operating head is computed and is initialized as a referenceposition.

The switching procedure of the encoder heads will now be described here,based on FIGS. 18A to 18E, with the switching from Y heads 64 ₃ to 64 ₄shown by arrow e₁ in FIG. 17A serving as an example.

FIG. 18A shows a state before the switching. In this state, Y head 64 ₃facing the scanning area (the area where the diffraction grating isarranged) on Y scale 39Y₂ is operating, and Y head 64 ₄ which has movedaway from the scanning area is suspended. The operating head isindicated here, using a solid black circle, and the suspended head isindicated by an outlined circle. Then, main controller 20 monitors themeasurement values of Y head 64 ₃ which is operating. The head whosemeasurement values are monitored, here, is shown in a double rectangularframe.

Then, when wafer stage WST moves in the +X direction, Y scale 39Y₂ isdisplaced in a direction to the right. In this case, in the embodiment,as is previously described, the distance between the Y heads is setsmaller than the effective width (width of the scanning area) of Y scale39Y₂ in the X-axis direction. Accordingly, as shown in FIG. 18B, a stateoccurs where both Y heads 64 ₃ and 64 ₄ face the scanning area of Yscale 39Y₂. Therefore, main controller 20 makes sure that Y head 64 ₄,which is suspended, has faced the scanning area along with Y head 64 ₃that is operating, and then activates the suspended Y head 64 ₄.However, main controller 20 does not yet start monitoring themeasurement values at this point.

Next, as shown in FIG. 18C, while Y head 64 ₃, which will be suspendedlater, faces the scanning area, main controller 20 computes a referenceposition of Y head 64 ₄, which has been restored, from the measurementvalues of the active encoder heads including Y head 64 ₃. Then, maincontroller 20 sets up the reference position as an initial value of themeasurement values of Y head 64 ₄. Incidentally, details on thecomputation of the reference position and the setting of the initialvalue will be described later in the description.

Main controller 20 switches the encoder head whose measurement valuesare monitored from Y head 64 ₃ to Y head 64 ₄ simultaneously with thesetting of the initial value above. After the switching has beencompleted, main controller 20 suspends the operation of Y head 64 ₃before it moves off the scanning area as shown in FIG. 18D. By theoperation described above, all the operations of switching the encoderheads are completed, and hereinafter, as shown in FIG. 18E, themeasurement values of Y head 64 ₄ are monitored by main controller 20.

In the embodiment, the distance between adjacent Y heads 65 and thedistance between adjacent Y heads 64 that head units 62A and 62Crespectively have are, for example, 70 mm (with some exceptions), andare set smaller than the effective width (e.g. 76 mm) of the scanningarea of Y scales 39Y₁ and 39Y₂ in the X-axis direction. Further, forexample, the distance between adjacent X heads 66 that head units 62Band 62D respectively have is, for example, 70 mm (with some exceptions),and is set smaller than the effective width (e.g. 76 mm) of the scanningarea of X scales 39X₁ and 39X₂ in the Y-axis direction. Accordingly, theswitching operation of Y heads 65 or 64 and X heads 66 can be performedsmoothly as in the description above.

Incidentally, the range in which both adjacent heads face the scale, ormore specifically, the moving distance of wafer stage WST from a stateshown in FIG. 18B to a state shown in FIG. 18D, for example, is 6 mm.And at the center, or more specifically, when wafer stage WST is locatedat the position shown in FIG. 18C, the head that monitors themeasurement values is switched. This switching operation is completed bythe time the head which is to be suspended moves off the scanning area,or more specifically, while wafer stage WST moves in an area by adistance of 3 mm during the state shown in FIG. 18C until the stateshown in FIG. 18D. For example, in the case the movement speed of thestage is 1 m/sec, then the switching operation of the head is to becompleted within 3 msec.

Next, the linkage process when the encoder head is switched, or morespecifically, the initial setting of the measurement values will bedescribed, focusing mainly on the operation of main controller 20.

In the embodiment, as is previously described, in the effective strokerange of wafer stage WST, three encoders (the X heads and the Y heads)constantly observe the movement of the stage so as to detect positionalinformation of wafer stage WST within the XY plane. Accordingly, whenthe switching process of the encoder is performed, wafer stage WST willbe observed in four encoder Enc1 to Enc4 which added the fourth encoder(a Y head) Enc4 as shown in FIG. 19.

In the switching state of the encoder shown in FIG. 19, encoders Enc1,Enc2, Enc3 and Enc4 are located above scales 39Y₁, 39Y₂, 39X₁, and 39Y₁,respectively. When having a look, it looks as though the encoder isgoing to be switched from encoder Enc1 to encoder Enc4. However, as isobvious from the fact that the position in the Y-axis direction, whichis the measurement direction, is different in encoder Enc1 and encoderEnc4, it does not have any meaning even if the measurement values ofencoder Enc1 are set without any changes as the initial value of themeasurement values of encoder Enc4 at the timing when the switching isperformed.

Therefore, in the embodiment, main controller 20 is made to switch fromposition measurement of wafer stage WST by the three encoders Enc1, Enc2and Enc3 to position measurement by the three encoders Enc2, Enc3 andEnc4, as shown in FIG. 19. In this switching method, the switching isperformed not from switching from one head to another head, but fromswitching from a combination of three heads (encoders) to a combinationof another three heads (encoders).

On the switching, first of all, main controller 20 solves thesimultaneous equations (25a) to (25c) using measurement values C₁, C₂,and C₃ of encoders Enc1, Enc2, and Enc3, and computes the positioncoordinate (X, Y, θz) of wafer stage WST within the XY plane. Next, byusing the position coordinate calculated here, main controller 20obtains theoretical value C₄ from the following theoretical formula(25d) which the measurement value of encoder (a Y head) Enc4 follows.

C ₄=−(p ₄ −X)sin θz+(q ₄ −Y)cos θz  (25d)

In this case, p₄ and q₄ are the X and Y setting positions of encoderEnc4. Then, theoretical value C₄ is set as an initial value of encoderEnc4. However, as is had been explained with formula (19), because themeasurement values of the encoder are discretized, theoretical value C₄is converted into a discrete value by a unit of measurement unitδ(=p/4n), or more specifically, into count value c₄=int(C₄/δ), and isset as the initial value of encoder Enc4. However, int(x/y)=[x−x % y]/y.The handling of remainder C₄%δ will be described later on.

By the linkage process described above, the switching operation of theencoder is completed while having maintained the results (X, Y, θz) ofposition measurement of wafer stage WST. From then onward, the followingsimultaneous equations (25b) to (25d) are solved, using the measurementvalues C₂, C₃, and C₄ of encoders Enc2, Enc3, and Enc4 which are usedafter the switching, and a position coordinate (X, Y, θz) of wafer stageWST is computed.

C ₂=−(p ₂ −X)sin θz+(q ₂ −Y)cos θz  (25b)

C ₃=(p ₃ −X)cos θz+(q ₃ −Y)sin θz  (25c)

C ₄=−(p ₄ −X)sin θz+(q ₄ −Y)cos θz  (25d)

Incidentally, in the case the fourth encoder is an X head, instead ofusing theoretical formula (25d), a simultaneous equation (25b) (25c)(25e), which uses the following theoretical formula (25e) can be used.

C ₄=(p ₄ −X)cos θz+(q ₄ −Y)sin θz  (25e)

However, various measurement errors are included in the actualmeasurement values (raw measurement values) of the encoders. Therefore,main controller 20 shows the value whose error has been corrected asmeasurement value C₄. Accordingly, in the linkage process describedabove, main controller 20 uses stage position induced error correctioninformation and/or correction information on the grating pitch of thescale (and correction information on the grating deformation) and thelike, and performs an inverse correction of theoretical value C₄obtained from formula (25d) or formula (25e) and computes raw value C₄′before correction, and then sets raw value C₄′ as the initial value ofthe measured value of encoder Enc4.

In the linkage process of the encoder, or more specifically, oncomputing and setting initial value C₄ of the fourth encoder, an errorcan occur. When exposure of all the shot areas on the wafer is actuallyperformed, the switching of the encoder will be performed, for example,around 100 times. Accordingly, even if the error which occurs in onelinkage process is small enough to ignore, the errors may be accumulatedby repeating the switching many times, and may come to exceed apermissible level. Incidentally, assuming that the errors occur atrandom, the cumulative error which occurs by performing the switching100 times is around 10 times the error which occurs when the switchingis performed once. Accordingly, the precision of the linkage processmust be improved as much as possible.

Therefore, the following two linkage methods, or more specifically, thecoordinate linkage method and the phase linkage method will beintroduced.

In the coordinate linkage method, first of all, from measurement valuesC₁, C₂, and C₃ of the three encoders Enc1, Enc2 and Enc3 before theswitching, the position coordinate (X, Y, θz) of wafer stage WST iscomputed via simultaneous equation (25a) to (25c). From the positioncoordinates, measurement value C₄ of the fourth encoder Enc4 ispredicted via formula (25d) (or formula (25e). And this initial value C₄is converted into a discrete value of measurement unit δ, or morespecifically, into δXc₄ (in this case, C₄ is a count value). Then, theposition coordinate is calculated back, by substituting sum δxc₄+dC₄ ofthe discrete value and minute amount dC₄ into C₄ on the left-hand sideof formula (25d) (or formula (25e)) and solving the simultaneousequations (25b) to (25d) (or, simultaneous equations (25b) (25c) (25e)).However, measurement values C₂ and C₃ are in common with the precedingones. Minute amount dC₄ is decided so that position coordinates (X′, Y′,θz′) obtained here coincide with position coordinates (X, Y, θz) whichhave been obtained earlier. Then, discrete value δxc₄ (count value c₄)is set in the fourth encoder Enc4 as the initial value. At the sametime, a phase offset is set to φ₀=φ′−2πdC₄/δ so as to correct phase φ′to phase 2πdC₄/δ, which corresponds to minute amount dC₄. In this case,minute amount dC₄ can be different from remainder C₄%δ due tocomputation errors or the like of the position coordinate of wafer stageWST using the simultaneous equations (25b) to (25d) (or, simultaneousequations (25b) (25c) (25e)).

In the coordinate linkage method, according to its principle, theposition coordinate of wafer stage WST that has been computed is storedwithout fail before and after the switching of the encoder. However, itmakes no difference in the error being accumulated each time the linkageprocess is repeated.

As was explained in detail based on FIGS. 18A to 18E, when the switchingprocess is performed between two adjacent encoders in the same headunit, the switching process is executed while the two encoderssimultaneously face the same scale. In this case, from the state where Yhead 64 ₄, which is the new head to be used, faces Y scale 39Y₂ as shownin FIG. 18B until the state where Y head 64 ₃, which is the head to besuspended later, moves off of Y scale 39Y₂ as shown in FIG. 18D, thereis a section of around 6 mm where the adjacent two heads face the samescale. In this case, the maximum movement speed of wafer stage WST is,for example, 1 m/sec, therefore, the time while the two adjacent headsface the same scale is around 6 msec or more. Therefore, performing thelinkage process will be considered while using the switching time tosecure sufficient linkage accuracy even if it is as short as around 6msec, rather than performing the linkage process as soon as thepreparations have been completed as is described in the example above.

The procedure will be explained, referring to examples shown in FIGS.18A to 18E. However, Y head 64 ₃ in the drawing corresponds to the firsthead (the first encoder) Enc1 which will be suspended later on, and Yhead 64 ₄ corresponds to the fourth head (the fourth encoder) Enc4 whichwill be newly used. As shown in FIG. 18B, when the fourth encoder Enc4(64 ₄) faces the scale (39Y₂), main controller 20 immediately restoresthe fourth encoder Enc4 (64 ₄). Then, according to the proceduredescribed above, main controller 20 predicts measurement value C₄ of thefourth encoder Enc4 (64 ₄), and provisionally sets an initial value (C₄and φ₀) determined by predicted value C₄ in the state shown in FIG. 18C,or more specifically, at a timing when the center of the adjacent twoencoders (64 ₃ and 64 ₄) is positioned at the center of the scale(39Y₂).

Now, in the example previously described, the encoders whose measurementvalues were monitored to compute the position coordinate of wafer stageWST were immediately switched after setting the initial value(performing the linkage process) from a first combination of Enc1, Enc2,and Enc3 to a second combination of Enc2, Enc3, Enc4. However, in thiscase, the switching is not yet performed, and prediction of measurementvalue C₄ of the fourth encoder Enc4 is still being performed. Then, maincontroller 20 obtains a difference ΔC₄, which is a difference of thepredicted value and the actual measurement value of the fourth encoderEnc4 in the provisional setting state, and the difference istime-averaged until the initial value of the fourth encoder Enc4 isactually set. Incidentally, as it will be described later on, becausethe measurement results of the encoder system are monitored at everypredetermined time interval in the embodiment, moving average is appliedto monitoring results of the predetermined number.

Difference ΔC₄ of the predicted value of measurement value C₄ of thefourth encoder Enc4 and the actual measurement value in the provisionalsetting state ideally takes a zero value, however, it actually becomesnonzero due to various causes of error. Furthermore, because most causesof error occur randomly with respect to time, the value of differenceΔC₄ fluctuates randomly as well with respect to the passage of time. Inthis case, by taking a time average of difference ΔC₄, an errorcomponent is averaged and the random fluctuation becomes smaller.Therefore, main controller 20 takes 6 msec or more of the switchingtime, and applies time average to difference ΔC₄. Then, after confirmingthat the fluctuation becomes small enough to be within a permissiblelevel, main controller 20 adds difference ΔC₄ to the provisionalpredicted value C₄ described earlier, and sets the initial values (C₄and φ₀) determined from predicted value C₄+ΔC₄ as the measurement valuesof the fourth encoder Enc4. After this main setting is completed, maincontroller 20 switches the encoders used to compute the positioncoordinate of wafer stage WST to the second combination Enc2, Enc3, andEnc4. Then, main controller 20 suspends the first encoder Enc1 when itmoves off away from the corresponding scale. This completes theswitching process.

In the case of the other method, or the phase linkage method, the basicsprocedure is the same as the coordinate linkage method describedearlier, however, the handling of the phase offset is different. In thecoordinate linkage method, the phase offset to the fourth encoder wasset again so that the position coordinate of wafer stage WST matchescompletely before and after the switching of the encoder. In the phaselinkage method, the phase offset will not be reset, and the phase offsetwhich is already set will be continuously used. More specifically, inthe phase linkage method, only the count value will be reset. In thiscase, the position coordinate of wafer stage WST which is computedbefore and after the switching of the encoder may be discontinuous.However, when the phase offset is set precisely, errors do not occurunless a setting error of the count value occurs. Accordingly,accumulation of errors by the repetition of the linkage process alsodoes not occur. Incidentally, as long as the setting procedure of thecount value previously described is followed, the possibility of thesetting error occurring is extremely low.

However, even if the phase offset is set precisely once, it may lose itsaccuracy due to a shift of the setting position of the encoder head andthe like occurring. Therefore, after the start-up of exposure apparatus100, the coordinate linkage method is applied at the time of the firstlinkage process so as to set the phase offset, and then at the time ofthe linkage process that follows, the phase linkage method is applied.Then, during an idle state of exposure apparatus 100 or at the beginningof a lot or the like, it is preferable to update the phase offset to thelatest value by appropriately performing the coordinate linkage method.

Studies of the inventor(s) and the like have recently revealed that whenwafer stage WST is driven in an accelerating manner, the scale isdistorted, which causes a measurement error in the encoder. Morespecifically, when the coordinate linkage method is applied and a phaseoffset is set during the movement of wafer stage WST in an acceleratingmanner, a linkage error occurs, which reduces the accuracy of the phaseoffset. Accordingly, it is not preferable to apply the coordinatelinkage method and to set the phase offset at the time of linkageprocess which occurs during the movement of wafer stage WST in anaccelerating manner. Therefore, for example, at the time of start up,during an idle state of exposure apparatus 100, or at the beginning of alot or the like, a sequence is to be performed to update the phaseoffset for of all or a part of the encoders (heads). However, in thissequence, the coordinate linkage method is to be performed by drivingwafer stage WST at a constant speed or having positioned wafer stage WSTat the linkage position without fail, so that an accurate phase offsetis set. Then, by switching the encoders by applying the phase linkagemethod at the time of exposure and at the time of alignment measurement,it becomes possible to constantly secure position measurement of waferstage WST with high precision.

Now, in the embodiment, the position coordinate of wafer stage WST iscontrolled by main controller 20 at a time interval of, for example, 96μsec. At each control sampling interval, a position servo control system(a part of main controller 20) updates the current position of waferstage WST, computes thrust command values and the like to position thestage to a target position, and outputs the values. As previouslydescribed, the current position of wafer stage WST is computed from themeasurement values of the interferometers or the encoders.

Now, as is previously described, intensity of the interference light ismeasured with the interferometer and the encoder. The measurement valuesare forwarded to main controller 20. Main controller 20 counts thenumber of times of intensity change of the interference light (morespecifically, the number of fringes of the interference light). And fromthe counter value (count value), the position of wafer stage WST iscomputed. Accordingly, main controller 20 monitors the measurementvalues of the interferometer and the encoder at a time interval(measurement sampling interval) much shorter than the control samplinginterval so as not to lose track of the fringes.

Therefore, in the embodiment, main controller 20 constantly continues toreceive the measurement values by a discharge from all the encoders (notalways three) that face the scanning area of the scales, while waferstage WST is within the effective stroke range. And, main controller 20performs the switching operation of the encoders described above (alinkage operation between a plurality of encoders) in synchronizationwith position control of wafer stage WST which is performed at eachcontrol sampling interval. In such an arrangement, an electricallyhigh-speed switching operation of the encoder will not be required,which also means that costly hardware to realize such a high-speedswitching operation does not necessarily have to be arranged.

FIG. 20 conceptually shows the timing of position control of wafer stageWST, the uptake of the measurement values of the encoder, and theswitching of the encoder in the embodiment. Reference code CSCK in thedrawing indicates the generation timing of a sampling clock (a controlclock) of the position control of wafer stage WST, and reference codeMSCK indicates a generation timing of a sampling clock (a measurementclock) of the measurement of the encoder (and interferometer). Further,reference code CH typically shows the switching (linkage) process of theencoder described in detail in FIGS. 18A to 18E.

Main controller 20 executes the switching of the encoder (head) bydividing the operation into two stages; the restoration and the linkageprocess of the encoder. When describing the switching according to anexample shown in FIG. 20, first of all, the encoders which are operatingat the time of the first control clock are the three encoders of thefirst combination, Enc1, Enc2 and Enc3. Main controller 20 monitors themeasurement value of these encoders, and computes the positioncoordinate (X, Y, θz) of wafer stage WST. Next, according to theposition coordinate of wafer stage WST, main controller 20 confirms allthe encoders which are on the scanning area of the X scales and the Yscales. And, from the encoders, main controller 20 specifies encoderEnc4 which needs restoration, and restores the encoder at the time ofthe second control clock. At this point in the process, the number ofoperating encoders becomes four. And, from the operating encoders, maincontroller 20 specifies the encoder whose measurement values are to bemonitored to compute the position coordinate of wafer stage WST at thetime of the next control clock, according to the position coordinate ofwafer stage WST. Assume that the second combination Enc2, Enc3 and Enc4are specified here. Main controller 20 confirms whether this specifiedcombination matches the combination that was used to compute theposition coordinate of wafer stage WST at the time of the previouscontrol clock. In this example, encoder Enc1 in the first combinationand encoder Enc4 in the second combination are different. Therefore, alinkage process CH to the second combination is performed at the time ofthe third control clock. Hereinafter, main controller 20 monitors themeasurement values of the second combination Enc2, Enc3 and Enc4, andcomputes the position coordinate (X, Y, θz) of wafer stage WST. As amatter of course, linkage process CH is not performed if there is nochange in the combination. Encoder Enc1 which is removed from themonitoring subject, is suspended at the time of the fourth control clockwhen encoder Enc1 moves off from the scanning area on the scale.

Main controller 20 performs scheduling of the encoder switching processfor each shot map (exposure map), and stores the results in memory 34.Accordingly, if there is no retry (redoing), then the contents of theschedule in every shot map becomes constant. However, in actualpractice, because a retry must be considered, it is preferable for maincontroller 20 to constantly update the schedule slightly ahead whileperforming the exposure operation.

Incidentally, so far, in order to describe the principle of theswitching method of the encoder to be used in position control of waferstage WST in the embodiment, four encoders (heads) Enc1, Enc2, Enc3 andEnc4 were taken up, however, encoders Enc1 and Enc2 representativelyshow any of Y heads 65 and 64 of head units 62A and 62C and Y heads 67and 68 of head units 62E and 62F, encoder Enc3 representatively shows Xhead 66 of head units 62B and 62D, and encoder Enc4 representativelyshow any of Y heads 65,64,67, and 68 or X head 66.

Incidentally, in the description so far, in order to simplify thedescription, while main controller 20 performed the control of each partof the exposure apparatus including the control of the stage, and theswitching (linkage) of the interferometer system, the encoder system,and the heads and the like, as a matter of course, at least a part ofthe control of main controller 20 described above can be performed,shared by a plurality of controllers. For example, a stage controllerwhich performs the control of the stage, the switching (linkage) of theinterferometer system, the encoder system and the heads and the like canbe arranged to operate under main controller 20.

As discussed in detail above, according to exposure apparatus 100related to the embodiment, the position (including the θz rotation) ofwafer stage WST within the XY plane (movement plane) is measured bythree encoders (heads), which at least include one each of an X encoderand a Y encoder of the encoder system. And, by main controller 20, theencoders (heads) used for position measurement of wafer stage WST isswitched from the first combination consisting of the three encoders tothe second combination consisting of three encoders that has at leastone encoder replaced to a different encoder from the previous threeencoders according to the movement of wafer stage WST. And, on thisswitching, by applying the coordinate linkage method and/or the phaselinkage method, main controller 20 initially sets the measurement valuesof the encoder (head) which is to be newly used (initial values of themeasurement vales are set). Accordingly, when viewing from a level whereerrors equal to or less than the measurement unit on the setting of theinitial values are not taken into consideration, the positioncoordinates of wafer stage WST computed from the measurement values ofthe encoder system are stored before and after the switching of theencoders (heads). Although the encoders (heads) used for positionmeasurement of wafer stage WST are constantly switched with the movementof wafer stage WST in this manner, an accurate linkage of the positioncoordinates of wafer stage WST becomes possible before and after theswitching. Accordingly, it becomes possible to move wafer stage WSTtwo-dimensionally accurately, while switching the plurality of encoders.

Especially in the case when main controller 20 sets the initial value ofthe measurement values of the encoders (heads) to be newly used, usingthe coordinate linkage method, the position coordinates of the waferstage can be saved before and after the switching (linkage) of theencoders.

Meanwhile, in the case when main controller 20 sets the initial value ofthe measurement values of the encoders (heads) to be newly used, usingthe phase linkage method, accumulation of errors can be prevented evenif the linkage process is repeated. Therefore, at the time of start up,during an idle state of exposure apparatus 100, or at the beginning of alot or the like, a sequence is performed to update the phase offset forof all or a part of the encoders (heads). However, in this sequence, thecoordinate linkage method is to be performed by driving wafer stage WSTat a constant speed or having positioned wafer stage WST at the linkageposition without fail, so that an accurate phase offset is set. Then, byswitching the encoders by applying the phase linkage method at the timeof exposure and at the time of alignment measurement, it becomespossible to constantly secure position measurement of wafer stage WSTwith high precision.

Further, according to exposure apparatus 100 of the embodiment, becausethe pattern of reticle R is transferred and formed on each of aplurality of shot areas on wafer W mounted on wafer stage WST which isdriven with good precision by the method described above while switchingbetween the plurality of encoders, it becomes possible to form a patternwith good precision on each shot area on wafer W. Especially, in theembodiment, because of the relative movement between illumination lightIL, which is irradiated on wafer W via reticle R and projection opticalsystem PL, and wafer W, wafer stage WST is driven with good precision bythe method described above while switching between the plurality ofencoders. Accordingly, it becomes possible to form a pattern on wafer Wwith good precision by scanning exposure.

Incidentally, the configuration of each measurement device such as theencoder system described in the embodiment above is only an example, andit is a matter of course that the present invention is not limited tothis. For example, in the embodiment above, an example has beendescribed where an encoder system is employed that has a configurationwhere a grid section (a Y scale and an X scale) is arranged on a wafertable (a wafer stage), and an X head and a Y head facing the gridsection is placed external to the wafer stage, however, the presentinvention is not limited to this, and as is disclosed in, for example,the U.S. Patent Application Publication No. 2006/0227309, an encodersystem which is configured having an encoder head arranged on the waferstage and has a grid section (for example, a two-dimensional grid, or alinear grid section having a two-dimensional placement) facing theencoder heads placed external to the wafer stage can also be adopted. Inthis case, a Z head can also be arranged on the wafer stage, and thesurface of the grid section can be a reflection surface on which themeasurement beam of the Z head is irradiated.

Further, in the embodiment above, while the case has been described, forexample, where the encoder head and the Z head were arranged separatelyinside head units 62A and 62C, a single head that has the function of anencoder head and a Z head can be used instead of a set of the encoderhead and the Z head.

Incidentally, in the embodiment above, an example was given where anoptical encoder by the diffraction interference method is used as theencoder, however, it is a matter of course that the movable body drivemethod and the movable body drive system related to the presentinvention can also be applied to a case where an encoder besides themethod described above is used. For example, a magnetic encoder can alsobe used.

Further, in the embodiment above, while the case has been describedwhere position measurement of wafer stage WST is performed by aninterferometer system and an encoder system, in the case reticle stageRST moves two-dimensionally as well as the measurement stage, an encodersystem having a configuration similar to the encoder system previouslydescribed can be arranged furthermore to measure the positionalinformation of reticle stage RST, and the switching of the heads and thelinkage can be performed in a procedure similar to the procedurepreviously described, using the coordinate linkage and/or phase linkageand the like as needed.

Incidentally, in the embodiment above, while the lower surface of nozzleunit 32 and the lower end surface of the tip optical element ofprojection optical system PL were substantially flush, as well as this,for example, the lower surface of nozzle unit 32 can be placed nearer tothe image plane (more specifically, to the wafer) of projection opticalsystem PL than the outgoing surface of the tip optical element. That is,the configuration of local liquid immersion device 8 is not limited tothe configuration described above, and the configurations can be used,which are described in, for example, EP Patent Application PublicationNo. 1 420 298, the pamphlet of International Publication No.2004/055803, the pamphlet of International Publication No. 2004/057590,the pamphlet of International Publication No. 2005/029559 (thecorresponding U.S. Patent Application Publication No. 2006/0231206), thepamphlet of International Publication No. 2004/086468 (the correspondingU.S. Patent Application Publication No. 2005/0280791), Kokai (JapaneseUnexamined Patent Application Publication) No. 2004-289126 (thecorresponding U.S. Pat. No. 6,952,253), and the like. Further, asdisclosed in the pamphlet of International Publication No. 2004/019128(the corresponding U.S. Patent Application Publication No.2005/0248856), the optical path on the object plane side of the tipoptical element may also be filled with liquid, in addition to theoptical path on the image plane side of the tip optical element.Furthermore, a thin film that is lyophilic and/or has dissolutionpreventing function may also be formed on the partial surface (includingat least a contact surface with liquid) or the entire surface of the tipoptical element. Incidentally, quartz has a high affinity for liquid,and also needs no dissolution preventing film, while in the case offluorite, at least a dissolution preventing film is preferably formed.

Incidentally, in the embodiment above, pure water (water) was used asthe liquid, however, it is a matter of course that the present inventionis not limited to this. As the liquid, a chemically stable liquid thathas high transmittance to illumination light IL and is safe to use, suchas a fluorine-containing inert liquid can be used. As thefluorine-containing inert liquid, for example, Fluorinert (the brandname of 3M United States) can be used. The fluorine-containing inertliquid is also excellent from the point of cooling effect. Further, asthe liquid, liquid which has a refractive index higher than pure water(a refractive index is around 1.44), for example, liquid having arefractive index equal to or higher than 1.5 can be used. As this typeof liquid, for example, a predetermined liquid having C—H binding or O—Hbinding such as isopropanol having a refractive index of about 1.50,glycerol (glycerin) having a refractive index of about 1.61, apredetermined liquid (organic solvent) such as hexane, heptane ordecane, or decalin (decahydronaphthalene) having a refractive index ofabout 1.60, or the like can be cited. Alternatively, a liquid obtainedby mixing arbitrary two or more of these liquids may be used, or aliquid obtained by adding (mixing) at least one of these liquids to(with) pure water may be used. Alternatively, as the liquid, a liquidobtained by adding (mixing) base or acid such as H+, Cs+, K+, Cl−,SO42−, or PO42− to (with) pure water can be used. Moreover, a liquidobtained by adding (mixing) particles of Al oxide or the like to (with)pure water can be used. These liquids can transmit ArF excimer laserlight. Further, as the liquid, liquid, which has a small absorptioncoefficient of light, is less temperature-dependent, and is stable to aprojection optical system (tip optical member) and/or a sensitive agent(or a protection film (top coat film), an antireflection film, or thelike) coated on the surface of a wafer, is preferable. Further, in thecase an F₂ laser is used as the light source, fomblin oil can beselected. Further, as the liquid, a liquid having a higher refractiveindex to illumination light IL than that of pure water, for example, arefractive index of around 1.6 to 1.8 may be used. As the liquid,supercritical fluid can also be used. Further, the tip optical elementof projection optical system PL may be formed by quartz (silica), orsingle-crystal materials of fluoride compound such as calcium fluoride(fluorite), barium fluoride, strontium fluoride, lithium fluoride, andsodium fluoride, or may be formed by materials having a higherrefractive index than that of quartz or fluorite (e.g. equal to orhigher than 1.6). As the materials having a refractive index equal to orhigher than 1.6, for example, sapphire, germanium dioxide, or the likedisclosed in the pamphlet of International Publication No. 2005/059617,or kalium chloride (having a refractive index of about 1.75) or the likedisclosed in the pamphlet of International Publication No. 2005/059618can be used.

Further, in the embodiment above, the recovered liquid may be reused,and in this case, a filter that removes impurities from the recoveredliquid is preferably arranged in a liquid recovery device, a recoverypipe or the like.

Incidentally, in the embodiment above, the case has been described wherethe exposure apparatus is a liquid immersion type exposure apparatus.However, the present invention is not limited to this, but can also beemployed in a dry type exposure apparatus that performs exposure ofwafer W without liquid (water).

Further, in the embodiment above, the case has been described where thepresent invention is applied to a scanning exposure apparatus by astep-and-scan method or the like. However, the present invention is notlimited to this, but may also be applied to a static exposure apparatussuch as a stepper. Even with the stepper or the like, by measuring theposition of a stage on which an object subject to exposure is mounted byencoders, generation of position measurement error caused by airfluctuations can substantially be nulled likewise. In this case, itbecomes possible to set the position of the stage with high precisionbased on correction information used to correct short-term fluctuationof the measurement values of the encoders using the measurement valuesof the interferometers and based on the measurement values of theencoders, and as a consequence, highly accurate transfer of a reticlepattern onto the object can be performed. Further, the present inventioncan also be applied to a reduction projection exposure apparatus by astep-and-stitch method that synthesizes a shot area and a shot area, anexposure apparatus by a proximity method, a mirror projection aligner,or the like. Furthermore, the present invention can also be applied to amulti-stage type exposure apparatus equipped with a plurality of waferstages, as is disclosed in, for example, Kokai (Japanese UnexaminedPatent Application Publication) No. 10-163099 and No. 10-214783 (thecorresponding U.S. Pat. No. 6,590,634), Kohyo (published Japanesetranslation of International Publication for Patent Application) No.2000-505958 (the corresponding U.S. Pat. No. 5,969,441), the U.S. Pat.No. 6,208,407, and the like.

Further, the magnification of the projection optical system in theexposure apparatus of the embodiment above is not only a reductionsystem, but also may be either an equal magnifying system or amagnifying system, and projection optical system PL is not only adioptric system, but also may be either a catoptric system or acatadioptric system, and in addition, the projected image may be eitheran inverted image or an upright image. Moreover, exposure area IA towhich illumination light IL is irradiated via projection optical systemPL is an on-axis area that includes optical axis AX within the field ofprojection optical system PL. However, for example, as is disclosed inthe pamphlet of International Publication No. 2004/107011, exposure areaIA may also be an off-axis area that does not include optical axis AX,similar to a so-called inline type catadioptric system, in part of whichan optical system (catoptric system or catadioptric system) that hasplural reflection surfaces and forms an intermediate image at least onceis arranged, and which has a single optical axis. Further, theillumination area and exposure area described above are to have arectangular shape. However, the shape is not limited to rectangular, andcan also be circular arc, trapezoidal, parallelogram or the like.

Incidentally, a light source of the exposure apparatus in the embodimentabove is not limited to the ArF excimer laser, but a pulse laser lightsource such as a KrF excimer laser (output wavelength: 248 nm), an F₂laser (output wavelength: 157 nm), an Ar₂ laser (output wavelength: 126nm) or a Kr₂ laser (output wavelength: 146 nm), or an extra-highpressure mercury lamp that generates an emission line such as a g-line(wavelength: 436 nm) or an i-line (wavelength: 365 nm) can also be used.Further, a harmonic wave generating device of a YAG laser or the likecan also be used. Besides the sources above, as is disclosed in, forexample, the pamphlet of International Publication No. 99/46835 (thecorresponding U.S. Pat. No. 7,023,610), a harmonic wave, which isobtained by amplifying a single-wavelength laser beam in the infrared orvisible range emitted by a DFB semiconductor laser or fiber laser asvacuum ultraviolet light, with a fiber amplifier doped with, forexample, erbium (or both erbium and ytteribium), and by converting thewavelength into ultraviolet light using a nonlinear optical crystal, canalso be used.

Further, in the embodiment above, illumination light IL of the exposureapparatus is not limited to the light having a wavelength equal to ormore than 100 nm, and it is needless to say that the light having awavelength less than 100 nm can be used. For example, in recent years,in order to expose a pattern equal to or less than 70 nm, an EUVexposure apparatus that makes an SOR or a plasma laser as a light sourcegenerate an EUV (Extreme Ultraviolet) light in a soft X-ray range (e.g.a wavelength range from 5 to 15 nm), and uses a total reflectionreduction optical system designed under the exposure wavelength (e.g.13.5 nm) and the reflective mask has been developed. In the EUV exposureapparatus, the arrangement in which scanning exposure is performed bysynchronously scanning a mask and a wafer using a circular arcillumination can be considered, and therefore, the present invention canalso be suitably applied to such an exposure apparatus. Besides such anapparatus, the present invention can also be applied to an exposureapparatus that uses charged particle beams such as an electron beam oran ion beam.

Further, in the embodiment above, a transmissive type mask (reticle) isused, which is a transmissive substrate on which a predetermined lightshielding pattern (or a phase pattern or a light attenuation pattern) isformed. Instead of this reticle, however, as is disclosed in, forexample, U.S. Pat. No. 6,778,257, an electron mask (which is also calleda variable shaped mask, an active mask or an image generator, andincludes, for example, a DMD (Digital Micromirror Device) that is a typeof a non-emission type image display device (spatial light modulator) orthe like) on which a light-transmitting pattern, a reflection pattern,or an emission pattern is formed according to electronic data of thepattern that is to be exposed can also be used.

Further, as disclosed in, for example, the pamphlet of InternationalPublication No. 01/035168, the present invention can also be applied toan exposure apparatus (lithography system) that forms line-and-spacepatterns on a wafer by forming interference fringes on the wafer.

Moreover, the present invention can also be applied to an exposureapparatus that synthesizes two reticle patterns on a wafer via aprojection optical system and almost simultaneously performs doubleexposure of one shot area by one scanning exposure, as is disclosed in,for example, Kohyo (published Japanese translation of InternationalPublication for Patent Application) No. 2004-519850 (the correspondingU.S. Pat. No. 6,611,316).

Further, an apparatus that forms a pattern on an object is not limitedto the exposure apparatus (lithography system) described above, and forexample, the present invention can also be applied to an apparatus thatforms a pattern on an object by an ink-jet method.

Incidentally, an object on which a pattern is to be formed (an objectsubject to exposure to which an energy beam is irradiated) in theembodiment above is not limited to a wafer, but may be other objectssuch as a glass plate, a ceramic substrate, a film member, or a maskblank.

The use of the exposure apparatus is not limited only to the exposureapparatus for manufacturing semiconductor devices, but the presentinvention can also be widely applied, for example, to an exposureapparatus for transferring a liquid crystal display device pattern ontoa rectangular glass plate, and an exposure apparatus for producingorganic ELs, thin-film magnetic heads, imaging devices (such as CCDs),micromachines, DNA chips, and the like. Further, the present inventioncan be applied not only to an exposure apparatus for producingmicrodevices such as semiconductor devices, but can also be applied toan exposure apparatus that transfers a circuit pattern onto a glassplate or silicon wafer to produce a mask or reticle used in a lightexposure apparatus, an EUV exposure apparatus, an X-ray exposureapparatus, an electron-beam exposure apparatus, and the like.

Incidentally, the movable body drive method and the movable body drivesystem of the present invention can be applied not only to the exposureapparatus, but can also be applied widely to other substrate processingapparatuses (such as a laser repair apparatus, a substrate inspectionapparatus and the like), or to apparatuses equipped with a movable bodysuch as a stage that moves within a two-dimensional plane such as aposition setting apparatus of a sample or a wire bonding apparatus inother precision machines.

Incidentally, the disclosures of the various publications, the pamphletsof the International Publications, and the U.S. Patent ApplicationPublication descriptions and the U.S. patent descriptions that are citedin the embodiment above and related to exposure apparatuses and the likeare each incorporated herein by reference.

Semiconductor devices are manufactured through the following steps: astep where the function/performance design of the wafer is performed, astep where a wafer is made using silicon materials, a lithography stepwhere the pattern formed on the reticle (mask) by the exposure apparatus(pattern formation apparatus) in the embodiment previously described istransferred onto a wafer, a development step where the wafer that hasbeen exposed is developed, an etching step where an exposed member of anarea other than the area where the resist remains is removed by etching,a resist removing step where the resist that is no longer necessary whenetching has been completed is removed, a device assembly step (includingprocesses such as a dicing process, a bonding process, and a packagingprocess), inspection steps and the like.

While the above-described embodiments of the present invention are thepresently preferred embodiments thereof, those skilled in the art oflithography systems will readily recognize that numerous additions,modifications, and substitutions may be made to the above-describedembodiments without departing from the spirit and scope thereof. It isintended that all such modifications, additions, and substitutions fallwithin the scope of the present invention, which is best defined by theclaims appended below.

1. A movable body drive method in which a movable body is driven along apredetermined plane including a first axis and a second axis orthogonalto each other, the method comprising: a first process in which aposition coordinate of the movable body is obtained, based onmeasurement values of three encoder heads among a plurality of firstencoder heads whose position in a direction parallel to the second axisis different and a plurality of second encoder heads whose position in adirection parallel to the first axis is different, with the threeencoder heads respectively facing three gratings selected from a pair offirst gratings whose periodic direction is in a direction parallel tothe first axis and a pair of second gratings whose periodic direction isin a direction parallel to the second axis that are arranged on asurface parallel to the predetermined plane of the movable body; and asecond process in which a measurement value of an encoder head to benewly used is set again so that the position coordinate is maintainedbefore and after the switching of the encoder head.
 2. The movable bodydrive method according to claim 1 wherein in the second process, onswitching a set of three encoder heads used in position control of themovable body to a different set of three encoder heads including atleast one encoder head which is different from the set of three encoderheads, a measurement value of an encoder head to be newly used is to beset again. 3-30. (canceled)
 31. A pattern formation method, comprising:a process in which an object is mounted on a movable body that can movein a movement plane; and a process in which the movable body is drivenby the movable body drive method according to claim 1, to form a patternto the object.
 32. A device manufacturing method including a patternformation process, wherein in the pattern formation process, a patternis formed on an object using the pattern formation method according toclaim
 31. 33. An exposure method in which a pattern is formed on anobject by an irradiation of an energy beam wherein for relative movementof the energy beam and the object, a movable body on which the object ismounted is driven, using the movable body drive method according toclaim
 1. 34. A movable body drive method in which a movable body isdriven along a predetermined plane including a first axis and a secondaxis orthogonal to each other, the method comprising: a first process inwhich a position coordinate of the movable body is obtained, based onmeasurement values of three encoder heads among a plurality of firstencoder heads whose position in a direction parallel to the second axisis different and a plurality of second encoder heads whose position in adirection parallel to the first axis is different, with the threeencoder heads respectively facing three gratings selected from a pair offirst gratings whose periodic direction is in a direction parallel tothe first axis and a pair of second gratings whose periodic direction isin a direction parallel to the second axis that are arranged on asurface parallel to the predetermined plane of the movable body; and asecond process in which only a measurement value by a measurement unitof an encoder head to be newly used after the switching is to be setagain, based on a position coordinate of the movable body.
 35. A patternformation method, comprising: a process in which an object is mounted ona movable body that can move in a movement plane; and a process in whichthe movable body is driven by the movable body drive method according toclaim 34, to form a pattern to the object.
 36. A device manufacturingmethod including a pattern formation process, wherein in the patternformation process, a pattern is formed on an object using the patternformation method according to claim
 35. 37. An exposure method in whicha pattern is formed on an object by an irradiation of an energy beamwherein for relative movement of the energy beam and the object, amovable body on which the object is mounted is driven, using the movablebody drive method according to claim
 34. 38. A movable body drive methodin which a movable body is driven along a predetermined plane includinga first axis and a second axis orthogonal to each other, the methodcomprising: a first process in which a position of the movable bodywithin the predetermined plane is controlled, based on measurementvalues of a set of heads of an encoder including three heads among aplurality of first heads whose position in a direction parallel to thesecond axis is different and a plurality of second heads whose positionin a direction parallel to the first axis is different, with the threeheads respectively facing three gratings selected from a pair of firstgratings whose periodic direction is in a direction parallel to thefirst axis and a pair of second gratings whose periodic direction is ina direction parallel to the second axis that are arranged on a surfaceparallel to the predetermined plane of the movable body; and a secondprocess in which a set of heads used in position control of the movablebody is switched to a different set of heads including three heads thathave at least one head which is different from the set of heads so thatthe position of the movable body within the plane becomes successivebefore and after the switching.
 39. The movable body drive methodaccording to claim 38 wherein the second process includes a specifyingprocess in which the three heads used in position control of the movablebody is specified based on positional information of the movable body; ajudgment process in which judgment is made of whether or not the threeheads which were specified are coincident with three heads of a set ofheads currently used in position control of the movable body; a decidingprocess in which when the heads are not coincident, an offset by ameasurement unit is decided by predicting a measurement value of aspecific head which is not currently used in position control of themovable body among the three specified heads based on the position ofthe movable body; a deciding process in which an offset equal to or lessthan the measurement unit of the specific head is decided based on theoffset by the measurement unit which has been decided so that theposition of the movable body is coincident before and after theswitching; and a changing process in which a set of heads used inposition control of the movable body is changed from the set of headscurrently used to the set of heads that are specified.
 40. The movablebody drive method according to claim 38, the method further comprising:a third process in which a set of heads used in position control of themovable body is switched to a different set of heads including threeheads that have at least one head which is different from the set ofheads, using the offset by the measurement unit computed based on theposition of the movable body and the offset equal to or less that themeasurement unit kept for each head.
 41. The movable body drive methodaccording to claim 38 wherein the switching of the set of heads isperformed from when the specific head used only after the switchingfaces the grating until the specific head which will not be used afterthe switching moves off of the grating.
 42. A pattern formation method,comprising: a process in which an object is mounted on a movable bodythat can move in a movement plane; and a process in which the movablebody is driven by the movable body drive method according to claim 38,to form a pattern to the object.
 43. A device manufacturing methodincluding a pattern formation process, wherein in the pattern formationprocess, a pattern is formed on an object using the pattern formationmethod according to claim
 42. 44. An exposure method in which a patternis formed on an object by an irradiation of an energy beam wherein forrelative movement of the energy beam and the object, a movable body onwhich the object is mounted is driven, using the movable body drivemethod according to claim
 38. 45. A movable body drive method in which amovable body is driven along a predetermined plane including a firstaxis and a second axis orthogonal to each other, the method comprising:a first process in which a position of the movable body within thepredetermined plane is controlled, based on measurement values of a setof heads of an encoder including three heads among a plurality of firstheads whose position in a direction parallel to the second axis isdifferent and a plurality of second heads whose position in a directionparallel to the first axis is different, with the three headsrespectively facing three gratings selected from a pair of firstgratings whose periodic direction is in a direction parallel to thefirst axis and a pair of second gratings whose periodic direction is ina direction parallel to the second axis that are arranged on a surfaceparallel to the predetermined plane of the movable body; and a secondprocess in which a set of heads used in position control of the movablebody is switched to a different set of heads including three heads thathave at least one head which is different from the set of heads, usingthe offset by the measurement unit computed based on the position of themovable body and the offset equal to or less than the measurement unitset for each head.
 46. The movable body drive method according to claim45 wherein the second process includes a specifying process in which thethree heads used in position control of the movable body is specified; ajudgment process in which judgment is made of whether or not the threeheads which were specified are coincident with three heads of a set ofheads currently used in position control of the movable body; and adeciding process in which when the heads are not coincident, an offsetby a measurement unit is decided by predicting a measurement value of aspecific head which is not currently used in position control of themovable body among the three specified heads based on the position ofthe movable body.
 47. The movable body drive method according to claim45 wherein the switching of the set of heads is performed from when thespecific head used only after the switching faces the grating until thespecific head which will not be used after the switching moves off ofthe grating.
 48. A pattern formation method, comprising: a process inwhich an object is mounted on a movable body that can move in a movementplane; and a process in which the movable body is driven by the movablebody drive method according to claim 45, to form a pattern to theobject.
 49. A device manufacturing method including a pattern formationprocess, wherein in the pattern formation process, a pattern is formedon an object using the pattern formation method according to claim 48.50. An exposure method in which a pattern is formed on an object by anirradiation of an energy beam wherein for relative movement of theenergy beam and the object, a movable body on which the object ismounted is driven, using the movable body drive method according toclaim
 45. 51. A movable body drive method in which a movable body isdriven along a predetermined plane including a first axis and a secondaxis orthogonal to each other, the method comprising: a first process inwhich a position of the movable body within the predetermined plane iscontrolled, based on measurement values of a set of heads of an encoderincluding three heads among a plurality of first heads whose position ina direction parallel to the second axis is different and a plurality ofsecond heads whose position in a direction parallel to the first axis isdifferent, with the three heads respectively facing three gratingsselected from a pair of first gratings whose periodic direction is in adirection parallel to the first axis and a pair of second gratings whoseperiodic direction is in a direction parallel to the second axis thatare arranged on a surface parallel to the predetermined plane of themovable body; a second process in which a set of heads used in positioncontrol of the movable body is switched to a different set of headsincluding three heads that have at least one head which is differentfrom the set of heads so that the position of the movable body withinthe predetermined plane becomes successive before and after theswitching, and also on the switching, a processing in which an offset bythe measurement unit of a specific head used only after the switching isdecided based on the position of the movable body, and an offset equalto or less than the measurement unit of the specific head is decidedbased on the decided offset by the measurement unit, so that theposition of the movable body is coincident before and after theswitching, with the plurality of first heads and/or the plurality ofsecond heads serving as the specific head; and a third process in whichuntil the offset equal to or less than the measurement unit is updated,a set of heads used in position control of the movable body is switchedat every timing when switching of the set of heads occurring with themovement of the movable body becomes required to a different set ofheads including three heads that have at least one head which isdifferent from the set of heads, using the offset by the measurementunit computed based on the position of the movable body and the offsetequal to or less than the measurement unit kept for each head.
 52. Themovable body drive method according to claim 51 wherein the processingin the second process is repeatedly performed each time a predeterminedcondition is satisfied.
 53. The movable body drive method according toclaim 51 wherein in the second process, on the switching of the set ofheads, the movable body is maintained in a state where acceleration iszero.
 54. The movable body drive method according to claim 51 whereinthe switching of the set of heads is performed from when the specifichead used only after the switching faces the grating until the specifichead which will not be used after the switching moves off of thegrating.
 55. A pattern formation method, comprising: a process in whichan object is mounted on a movable body that can move in a movementplane; and a process in which the movable body is driven by the movablebody drive method according to claim 51, to form a pattern to theobject.
 56. A device manufacturing method including a pattern formationprocess, wherein in the pattern formation process, a pattern is formedon an object using the pattern formation method according to claim 55.57. An exposure method in which a pattern is formed on an object by anirradiation of an energy beam wherein for relative movement of theenergy beam and the object, a movable body on which the object ismounted is driven, using the movable body drive method according toclaim
 51. 58. A movable body drive system in which a movable body isdriven along a predetermined plane including a first axis and a secondaxis orthogonal to each other, the system comprising: a pair of firstgratings whose periodic direction is in a direction parallel to thefirst axis and a pair of second gratings whose periodic direction is ina direction parallel to the second axis that are arranged on a surfaceparallel to the predetermined plane of the movable body; a first encodersystem which has a plurality of first heads whose positions aredifferent in a direction parallel to the second axis and measurespositional information of the movable body in a direction parallel tothe first axis, based on measurement values of the first headsrespectively facing the pair of first gratings; a second encoder systemwhich has a plurality of second heads whose positions are different in adirection parallel to the first axis and measures positional informationof the movable body in a direction parallel to the second axis, based onmeasurement values of the second heads respectively facing the pair ofsecond gratings; and a controller which obtains a position coordinate ofthe movable body within the predetermined plane based on measurementvalues of a set of heads including three heads respectively facing threegratings selected from the pair of first gratings and the pair of secondgratings, and sets a measurement value again of a head which is to benewly used so that the position coordinate is maintained before andafter the switching when switching the head to be used in positionmeasurement of the movable body.
 59. The movable body drive systemaccording to claim 58 wherein the controller sets a measurement valueagain of a head which is to be newly used when switching a set of threeheads used in position control of the movable body to a different set ofheads including three heads that have at least one head different fromthe set of three heads.
 60. The movable body drive system according toclaim 59 wherein the controller sets a measurement value by ameasurement unit according to a head which is to be newly used after theswitching, based on a position coordinate of the movable body.
 61. Themovable body drive system according to claim 59 wherein the controllerobtains a position coordinate of the movable body in the predeterminedplane, based on the measurement values of the set of heads including thethree heads respectively facing the three gratings selected from thepair of first gratings and the pair of second gratings, and can drivethe movable body by performing switching of a first mode in which ameasurement value of a head to be newly used is set again so that theposition coordinate is maintained before and after the switching of thehead and a second mode in which only a measurement value by ameasurement unit according to a head to be newly used after theswitching is set again.
 62. A pattern formation apparatus, comprising:the movable body drive system according to claim 58 that drives themovable body on which an object is mounted, for pattern formation to theobject; and a pattern generation system which generates a pattern on theobject.
 63. An exposure apparatus that forms a pattern on an object byan irradiation of an energy beam, the apparatus comprising: a patterningdevice that irradiates the energy beam on the object; and the movablebody drive system according to claim 58, whereby the movable body drivesystem drives the movable body on which the object is mounted forrelative movement of the energy beam and the object.
 64. A movable bodydrive system in which a movable body is driven along a predeterminedplane including a first axis and a second axis orthogonal to each other,the system comprising: a pair of first gratings whose periodic directionis in a direction parallel to the first axis and a pair of secondgratings whose periodic direction is in a direction parallel to thesecond axis that are arranged on a surface parallel to the predeterminedplane of the movable body; a first encoder system which has a pluralityof first heads whose positions are different in a direction parallel tothe second axis and measures positional information of the movable bodyin a direction parallel to the first axis, based on measurement valuesof the first heads respectively facing the pair of first gratings; asecond encoder system which has a plurality of second heads whosepositions are different in a direction parallel to the first axis andmeasures positional information of the movable body in a directionparallel to the second axis, based on measurement values of the secondheads respectively facing the pair of second gratings; and a controllerwhich obtains a position coordinate of the movable body in thepredetermined plane, based on the measurement values of the set of headsincluding the three heads respectively facing the three gratingsselected from the pair of first gratings and the pair of secondgratings, and sets only a measurement value by a measurement unitaccording to a head to be newly used after the switching again, based onthe position coordinate when switching the head to be used for positionmeasurement of the movable body.
 65. A pattern formation apparatus,comprising: the movable body drive system according to claim 64 thatdrives the movable body on which an object is mounted, for patternformation to the object; and a pattern generation system which generatesa pattern on the object.
 66. An exposure apparatus that forms a patternon an object by an irradiation of an energy beam, the apparatuscomprising: a patterning device that irradiates the energy beam on theobject; and the movable body drive system according to claim 64, wherebythe movable body drive system drives the movable body on which theobject is mounted for relative movement of the energy beam and theobject.
 67. A movable body drive system in which a movable body isdriven along a predetermined plane including a first axis and a secondaxis orthogonal to each other, the system comprising: a pair of firstgratings whose periodic direction is in a direction parallel to thefirst axis and a pair of second gratings whose periodic direction is ina direction parallel to the second axis that are arranged on a surfaceparallel to the predetermined plane of the movable body; a first encodersystem which has a plurality of first heads whose positions aredifferent in a direction parallel to the second axis and measurespositional information of the movable body in a direction parallel tothe first axis, based on measurement values of the first headsrespectively facing the pair of first gratings; a second encoder systemwhich has a plurality of second heads whose positions are different in adirection parallel to the first axis and measures positional informationof the movable body in a direction parallel to the second axis, based onmeasurement values of the second heads respectively facing the pair ofsecond gratings; and a controller which controls the position of themovable body in the predetermined plane, based on the measurement valuesof the set of heads including the three heads respectively facing thethree gratings selected from the pair of first gratings and the pair ofsecond gratings, and also switches a set of heads used in positioncontrol of the movable body to a different set of heads including threeheads that have at least one head which is different from the set ofheads so that the position of the movable body within the predeterminedplane becomes successive before and after the switching.
 68. The movablebody drive system according to claim 67 wherein to switch the set ofheads, the controller specifies the three heads used in position controlof the movable body based on positional information of the movable body,and judges whether or not the three heads which were specified arecoincident with three heads of a set of heads currently used in positioncontrol of the movable body, and when the heads are not coincident,decides an offset by a measurement unit by predicting a measurementvalue of a specific head which is not currently used in position controlof the movable body among the three specified heads based on theposition of the movable body, and based on the offset by the measurementunit which has been decided, decides an offset equal to or less than themeasurement unit of the specific head so that the position of themovable body is coincident before and after the switching.
 69. Themovable body drive system according to claim 68 wherein the controllerfurthermore switches a set of heads used in position control of themovable body to a different set of heads including three heads that haveat least one head which is different from the set of heads, using theoffset by the measurement unit computed based on the position of themovable body and the offset equal to or less than the measurement unitkept for each head.
 70. The movable body drive system according to claim67 wherein the controller performs the switching of the set of headsfrom when the specific head used only after the switching faces thegrating until the specific head which will not be used after theswitching moves off of the grating.
 71. A pattern formation apparatus,comprising: the movable body drive system according to claim 67 thatdrives the movable body on which an object is mounted, for patternformation to the object; and a pattern generation system which generatesa pattern on the object.
 72. An exposure apparatus that forms a patternon an object by an irradiation of an energy beam, the apparatuscomprising: a patterning device that irradiates the energy beam on theobject; and the movable body drive system according to claim 67, wherebythe movable body drive system drives the movable body on which theobject is mounted for relative movement of the energy beam and theobject.
 73. A movable body drive system in which a movable body isdriven along a predetermined plane including a first axis and a secondaxis orthogonal to each other, the system comprising: a pair of firstgratings whose periodic direction is in a direction parallel to thefirst axis and a pair of second gratings whose periodic direction is ina direction parallel to the second axis that are arranged on a surfaceparallel to the predetermined plane of the movable body; a first encodersystem which has a plurality of first heads whose positions aredifferent in a direction parallel to the second axis and measurespositional information of the movable body in a direction parallel tothe first axis, based on measurement values of the first headsrespectively facing the pair of first gratings; a second encoder systemwhich has a plurality of second heads whose positions are different in adirection parallel to the first axis and measures positional informationof the movable body in a direction parallel to the second axis, based onmeasurement values of the second heads respectively facing the pair ofsecond gratings; and a controller which controls the position of themovable body in the predetermined plane, based on the measurement valuesof the set of heads including the three heads respectively facing thethree gratings selected from the pair of first gratings and the pair ofsecond gratings, and also switches a set of heads used in positioncontrol of the movable body to a different set of heads including threeheads that have at least one head which is different from the set ofheads, using the offset by the measurement unit computed based on theposition of the movable body and the offset equal to or less than themeasurement unit kept for each head.
 74. The movable body drive systemaccording to claim 73 wherein to switch the set of heads, the controllerspecifies the three heads used in position control of the movable bodybased on positional information of the movable body, and judges whetheror not the three heads which were specified are coincident with threeheads of a set of heads currently used in position control of themovable body, and when the heads are not coincident, an offset by ameasurement unit is decided by predicting a measurement value of aspecific head which is not currently used in position control of themovable body among the three specified heads based on the position ofthe movable body.
 75. The movable body drive system according to claim74 wherein to switch the set of heads, the controller furthermore setsan offset equal to or less than the measurement unit of the specifichead based on the offset by the measurement unit which has been decided,so that the position of the movable body is coincident before and afterthe switching each time a predetermined condition is satisfied.
 76. Themovable body drive system according to claim 75 wherein the controllerperforms the switching of the set of heads while maintaining the movablebody in a state where acceleration is zero.
 77. The movable body drivesystem according to claim 73 wherein the controller performs theswitching of the set of heads from when the specific head used onlyafter the switching faces the grating until the specific head which willnot be used after the switching moves off of the grating.
 78. A patternformation apparatus, comprising: the movable body drive system accordingto claim 73 that drives the movable body on which an object is mounted,for pattern formation to the object; and a pattern generation systemwhich generates a pattern on the object.
 79. An exposure apparatus thatforms a pattern on an object by an irradiation of an energy beam, theapparatus comprising: a patterning device that irradiates the energybeam on the object; and the movable body drive system according to claim73, whereby the movable body drive system drives the movable body onwhich the object is mounted for relative movement of the energy beam andthe object.